There is no limit because there is no way a limit can be set. Citizenship is controlled by each country. There is no nation that can say “only x number of nations can offer citizenship to one person”.

All they can do is define who CAN have their citizenship.

They can also prohibit their citizens from holding another citizenship but those people themselves do not necessarily have control over what citizenship they hold, because it is up to each nation to determine who are its citizens, it’s not the citizens’ decision unless national law makes it a choice.

You do have nations that will take your citizenship if they know you have acquired another. But there is no unity about that or standard process for telling and some nations won’t let you renounce your citizenship.

Under US law you can hardly do anything that will cause you to lose your citizenship unless you WANT to lose it. Even if you get naturalized in another nation you remain a US Citizen and even if THAT nation requires you to renounce your US citizenship the US won’t do it unless you WANT to lose it. And when you sign your US Citizenship oath saying you renounce all other allegiances, guess what? It means nothing. You can keep on using your other passports anywhere but in the US.

As a purely practical matter I can envision how one might have as many as 8 or even a few more citizenships. It is likely if you have more you don’t know about them. There can be advantages to having several but at some point the cost of passports for all those nations gets pretty significant.

There is no such numerical limits. First of all one needs to look at the country. All have their own rules, even within the EU. Some countries strictly disallow multiple citizenships; if one gets another then they lose the one from that country. And then one has to look at the situation like having a citizenship by birthright or by naturalization. Often a birthright to multiple citizenships in not a problem but one has to give up or loses a citizenship by naturalizing elsewhere. This makes it difficult for people to acquire many citizenships, conflicting rules and the time and requirements one needs to successfully naturalize somewhere. But theoretically one could be born with handful or more citizenships – and maybe add another one or two later. Rules are made that state the conditions for citizenship and while they might disallow any others, they will never say one can have say 3 or 4 or 5 as a limit.

Dual citizenship by region

• Africa:

Some African countries restrict or forbid dual citizenship.

It is allowed for example in Angola, Burundi, Côte d'Ivoire, Djibouti, Gabon, Gambia, Ghana, Kenya, Mali, Morocco, Mozambique, Niger, Nigeria, Rwanda, Senegal, São Tomé and Príncipe, Sierra Leone, Sudan, Tunisia, and Uganda.Eritreans, Egyptians, and South Africans wanting to take another citizenship need a permission to maintain their citizenship. Eritrea taxes its citizens worldwide, even if they have never lived in the country.Lesotho restricts dual citizenship, but observes jus soli.

• The Americas:

Most American countries allow dual citizenship (some only for citizens by descent or with other American countries with which they have agreements). Some countries (e.g., Argentina, Bolivia, Costa Rica) do not allow their citizens to renounce their citizenship, so they keep it even when naturalizing in a country that forbids dual citizenship. Most American countries observe unconditional jus soli, i.e. a child born there is regarded as a citizen even if the parents are not. Some countries (Dominican Republic, Ecuador, Guatemala, Honduras, Mexico, Nicaragua, Uruguay) allow renunciation of citizenship only if it was involuntarily acquired by birth to non-citizen parents.

Canada and the United States allow dual citizenship and are worldwide the only two developed economies to grant unconditional birthright citizenship. The United States taxes its citizens and Green-Card holders worldwide, even if they have never lived in the country. In 2015, the fee for renunciation of U.S. citizenship was raised to $2,350 - the highest citizenship-renuciation fee worldwide.

Dual citizenship is restricted or forbidden, for example, in Cuba, Haiti and Suriname.

• Asia-Pacific:

Most countries in the Asia-Pacific region restrict or forbid dual citizenship. But in some of these countries (e.g. Iran, North Korea, Thailand), it is very difficult or even impossible for citizens to renounce their citizenship, even when naturalizing in another country.

Dual citizenship is allowed for example in Australia, Fiji, New Zealand, Philippines, Samoa, Tonga, and Vanuatu.

Cambodia allows dual citizenship and observes jus soli for children born to legal permanent residents born in Cambodia or to children whose parents are unknown.

South Korea allows dual citizenship in limited circumstances. It allows foreign born nationals who married to a Korean citizen, Korean men holding dual citizenship by birth who served in the Republic of Korea Armed Forces as compulsory military service, Korean women with multiple nationalities by birth who has vowed her intention not to exercise her foreign nationality in the Republic of Korea by the age of 22 and overseas Koreans at least 65 years of age.

Taiwan and Hong Kong allow dual citizenship for citizens by birth, but do not permit applicants for naturalization to retain their prior citizenship.

Burmese nationality law forbids its citizens to have dual citizenship, and foreigners cannot become naturalized citizens, unless they can prove a close familial connection to the country

Pakistan restricts dual citizenship, but observes jus soli.

In Papua New Guinea there was overwhelming support from parliament to amend their Constitution to allow dual citizenship, however the law had yet to come into force as of February 2014.

Sri Lanka allows dual citizenship. However, under the 19th amendment of that country's constitution, dual citizens are not allowed to hold public office.

Israel allows dual citizenship.

Indian constitution does not allow voluntary Dual Citizenship.However, in response to persistent demands for dual citizenship, particularly from the diaspora in North America and other developed countries, the The Overseas Citizenship of India (OCI) scheme was introduced by amending The Citizenship Act, 1955 in August 2005.

• The rest of Europe other than EU, EFTA, and microstates:

Albania,Belarus,Moldova,Russia and Serbia allow dual citizenship. But in Russia, a second citizenship must be reported.Bosnia,Macedonia, and Montenegro generally do not allow dual citizenship.

Ukrainian law currently does not recognise dual citizenship. However there are citizens of Ukraine who hold dual citizenship. This includes state officials such as Igor Kolomoisky, who holds three citizenships. On February 8, 2014, the Rada proposed a bill to criminalize the act of holding two citizenships

Yes and no.

The “no” first. No countries have laws saying “you can only have three, five, twenty-nine, or so-many citizenships”. So long as you’re willing to go through the process of acquiring a new citizenship (which is going to average some 5 years of living in a different place, learning the language, getting your head around the culture, etc), go for your life.

But then there’s the “yes”. And that “yes” is that several countries have laws saying “you can’t have dual citizenship in the first place.” If you’re a citizen of one of those countries, you can’t maintain that citizenship if you naturalise elsewhere - even if that second country doesn’t care about such matters.

There’s also the fact that people don’t tend to live long enough to be able to acquire citizenships endlessly (and very few are interested in such a - forgive the term - pissing contest). It becomes considerably harder to acquire a new citizenship after you’ve retired, for example, as many countries want you to be earning money there legally, rather than collecting a foreign pension.

Theoretically there's no upper limit.

Some countries prohibit dual citizenship completely, for example the People's Republic of China (Excluding the Special Administrative Regions of Hong Kong and Macau) completely prohibits its citizens from holding any other citizenship.

Other countries prohibit people from obtaining another citizenship if not by birth. For example if somebody were born in Canada to Austrian parents, he would have both Austrian and Canadian citizenship. However, if he were to move to the US and naruralise there he would lose his Austrian citizenship as Austria does not allow for that (unless he applied for permission which may be granted if either he is considered a benefit to Austria - Arnold Schwarzenegger has dual Austrian-American citizenship for this very reason - or there are significant personal reasons for it), leaving him only a US and Canadian citizen.

Then there are the countries that don't care about dual citizenship, and will let foreigners naturalise without having to renounce their previous citizenship, and will let their citizens naturalise abroad with no repercussions.

These are the main three approaches to dual citizenship. Some countries only allow it with certain other ones (Such as Germany which allows it with EU countries and Switzerland, but prohibits it in most other cases), others allow potential citizens to retain their original citizenship but does not allow them to obtain any other nationalities once naturalised but may potentially allow citizens at birth to naturalise abroad (South Africa is an example of this).

As such there's no firm upper limit to the number of citizenships an individual may hold, but it's limited by countries. To calculate it would take a long long time with lots of research being involved. It also depends on how many nationalities one counts. Does Taiwan count? What about Palestine? Kosovo? And what about Transnistria?

There are 195 countries (or thereabouts)

Of those; at least 65 specifically allow dual/( multi) citizenship.

There are others that don’t really care, and a few that specifically do not.

So you could clearly legally have 65 citizenships.

But most countries require a minimum permanent residency of 5 years ( in some cases, 10, 20, or even 30) before citizenship can be granted. There are one or two where you can “ buy “ it directly)

So assuming 5 years residency criteria, and if you started collecting citizenships at age 18 and lived to age 90, you could theoretically get about 14.

Though in reality, that would not be possible.

I know one person who has 5, and three “ triple citizens” .

Dual citizenship is very vague issue. In one hand, there is really no limit on a person as to how many instances of citizenship one can maintain. The real concern comes from the country you wish to hold citizenship with.

They must allow and recognize your various claims from other countries.

A country can be a jealous Mistress. They want your love and loyalty alone and are not eager to share. This also means that those countries must play well together on the school yard. The United States Of America has strained relations at best with some Middle Eastern countries. As a result, such requests for dual citizenship would be denied.

He who dies with the most citizenship documents does not win anything.

As Mr. Gordon noted, a country either allows or does not allow its nationals to hold other citizenships. If it allows this, then there is no limit.

So far the most citizenships that I have ever seen a client have is 8

-Cape Verde (through economic citizenship)
-Belize (though economic citizenship)
-Dominica (through economic citizenship)
-Grenada (through economic citizenship)
-St. Kitts and Nevis (through economic citizenship)
-Ireland (through lineage)
-Canada (through naturalization)
-UK (through naturalization in a British Overseas Territory)

It would have been nine but he renounced his US citizenship for tax purposes after acquiring his first new citizenship. Obviously he had gone well beyond prudent diversification of his "Passport Portfolio" and into the realm of hobby collection. I do have to say that he finally seems satisfied as he declined when I asked if he would like Cyprus (economic). By that point he already had 2 EU citizenships.

For me, I will say St.kitts and Nevis（I have an application got approval in 38 days with total cost of US$110,000）

(a small caribbean country with 159 visa-free countries),

here you just pay your money and buy your citizenship.

Actually St.kitts has two options that you can get your citizenship which are donation and buying real estate property.

Donation option is that you donate US$150K to St.kitts SDF(Process is you submit your documents first and pay the 150k after your application get approval)

Real estste option is that you pay US$200K(you will own a unit with another investor under this option) or US$400K(you will own your unit yourself).

There is a new option except the above two options, a financing way to obtain St.kitts citizenship, which is you pay (US$60,000 plus government fees, lawyer fees etc) around US110,000 to get citizenship, US110,000 is you total cost to get the citizenship.

St.kitts citizenship application process will take around 3–4 months from 0 to get your St.kitts passport(you do not need to come here during the whole process)

I actually talked with the CEO of Citizenship Investment By Unit of St.kitts interms of the history of St.kitts citizenship and his efforts to market st.kitts citizenship, he told me that St.kitts Citizenship Investment By Unit had made their work the most efficient(fast due diligence process, actually less than 3 months to get your citizenship application approval) during all competitors becase of too many competitors(Turkey and other cariibean countries.)

Multiple citizenship, also called dual citizenship or multiple nationality or dual nationality, is a person's citizenship status, in which a person is concurrently regarded as a citizen of more than one state under the laws of those states. There is no international convention which determines the nationality or citizen status of a person, which is defined exclusively by national laws, which vary and can be inconsistent with each other. Multiple citizenship arises because different countries use different, and not necessarily mutually exclusive, criteria for citizenship. Colloquial speech refers to people "holding" multiple citizenship but technically each nation makes a claim that this person be considered its national.

Some countries do not permit dual citizenship. This may be by requiring an applicant for naturalisation to renounce all existing citizenship, or by withdrawing its citizenship from someone who voluntarily acquires another citizenship, or by other devices. Some countries do not permit a renunciation of citizenship. Some countries permit a general dual citizenship while others permit dual citizenship but only of a limited number of countries.

Most countries that permit dual citizenship still may not recognize the other citizenship of its nationals within its own territory, for example, in relation to entry into the country, national service, duty to vote, etc. Similarly, it may not permit consular access by another country for a person who is also its national. Some countries prohibit dual citizenship holders from serving in their military, on police forces or holding certain public offices.

There is not a clear answer to that question.

Each sovereign country decides independently who is a citizen (or a national) of that respective country. In fact, that is one of the attributes of sovereignty. Some countries allow their citizens or nationals to hold multiple citizenships or nationalities in other countries without losing/forefeiting their domestic citizenship or nationality. Others do not and will automatically cancel your citizenship or nationality if, for example, you become a naturalized citizen of another country voluntarily. Conversely, some countries might demand that you renounce your original citizenship before you can be naturalized in their jurisdiction. Sometimes, renunciation might be impossible though in the law of your country of origin.

So I guess a possible answer is that, in principle, you can be a citizen or national of as many countries as those that recognize such citizenship or nationality, but, if either your original country, or a foreign country where you are seeking citizenship, does not allow dual citizenship, then you will have to choose one.

In general, in countries like the UK, Australia, Canada, or the US, you can now hold multiple citizenships with no penalty in the law. In fact, many people do in the US for example, not so much by becoming a naturalized citizen of some other country, but rather by being born in the USA to parents from other countries that recognize citizenship by descent, or by being born yourself in another country and then becoming a naturalized U.S. citizen.

Depends on the country. Some do not allow dual citizenship, others do. If you hold multiple citizenship, then one country CANNOT do anything for you if you are a citizen of that country as well.

i.e. if you get arrested in Mexico and are an American Citizen, then the US Government can discuss with the Mexican authorities to make sure you are not being tortured, and are getting medical treatment. But if you are also a Mexican citizen, then they cannot - if you are being branded with electrical prodding rods the US won’t interfere, because, hey, after all you WANTED to be Mexican.

There was a Canadian of Greek Cypriot extraction that went back to Cyprus to visit his ancestral home. But by Greek Cypriot law, children of Greek Cypriots are citizens of Cyprus even if born in another country. So when this Canadian (he had been born in Canada) arrived in Cyprus, the Cypriot authorities put him in the Greek Cypriot Army (they have the draft in Cyprus) and the Canadian Embassy couldn’t do anything because according to Greek Cypriot law he was a citizen.

In the end, the Canadian military talked with the Greek Cypriot Military and a truck this chap was in just happened to park at a certain roadside restaurant where it so happened a Canadian military convoy (part of the UN force in Cyprus at the time) stopped as well. He just happened to ‘wander off’ and get in the wrong truck. The Canadian military denied any knowledge of the lad, even while he was boarding the Canadian military weekly fight out of Cyprus. It pays to have friends in the military

So in relation to your question, having multiple citizenships can be hazardous to your health and welfare.

I don't think there is any set limit other than the number of countries that permit other citizenships.

If for example Alan from Hungary and Amelia from Italy give have a daughter born in Belfast before 1983, then Betty would have 4 citizenships that she can pass on by descent; Hungarian, Italian, British and Irish. If Betty meets Bob who's in a similar situation and they have a child born in a birthright citizenship country (eg Canada) then the child will have 9 citizenships at birth, and that's not including countries where great grandparents can pass on citizenship. That assumes that Betty and Bob haven't naturalised a couple of citizenships, that can be passed on by descent. After birth, new citizens could be built up approximately every five years.

There appear to be 40 countries that allow dual citizenship without restrictions (Countries That Allow or Disallow Dual Citizenship - D'Alessio Law Group).

As a practical matter, being resident in so many countries long enough in one lifetime isn’t possible, but you can gain citizenship through your parents. If you, your children, and grand-children all dedicated your lives to making this happen, I think your great grand-children could collect all 40. (Of course, by that time the rules in various countries will have changed, so it might be a different 40, or maybe there will be a few more countries you need to collect.).

In theory, hundreds (all of the ones that don’t disallow dual/multiple citizenships).
In practice, maybe a dozen? Under the right circumstances, you could be born with 7 or 8 or so (one from each grandparent, one more from each parent, one from the country where you’re born, maybe squeeze in a few extra if your parents naturalized into more than one country) and then you could naturalize into a few more, but the naturalization process generally takes years, and life is only so long. Of course, if you have enough money, there are citizenship by investment programs, so you could (basically) purchase a few more.

As an American, the answer is that to become an American Citizen, one must renounce all other citizenships. The Oath of naturalization begins,

"I hereby declare, on oath, that I absolutely and entirely renounce and abjure all allegiance and fidelity to any foreign prince, potentate, state, or sovereignty, of whom or which I have heretofore been a subject or citizen; that I will support and defend the Constitution and laws of the United States of America against all enemies, foreign and domestic; that I will bear true faith and allegiance to the same; …”

Nevertheless, recent U.S. practice, created by various court decisions and not the legislature, is to allow dual citizenship. The intent and practice of naturalization was corrupted by courts, in defiance of the law.

It is noteworthy that in many places, the US Constitution refers to people under US “jurisdiction”. This excludes people who are not solely American Citizens, who have allegiance to some foreign nation. It was not intended by the framers of our Constitution that a person could be an American Citizen and also be a British Subject. This creates conflict of loyalties and messy international law situations. America fought the bloody War of 1812, for example, to force Britain to stop enforcing its laws on Americans who had been born to a British Father ( who were thus subjects to the British King ).

(Standard disclaimer: these are my ideas alone and do not represent the views of the U.S. government or any of its offices or agencies.)

When I went through Consular tradecraft and we discussed passports and nationality, I hypothesized about the possibility of someone being born with multiple citizenships as the result of a bizarre confluence of events. It went like this:

Pregnant mother (already at nearly 8 months) has two citizenships, both of which are transmitted to any children at birth by virtue of the laws of those countries. Father-to-be has two different citizenships, ditto. They take off from a country whose citizenship and nationality laws say anyone born on a flight originating in that country, regardless of where it lands, is entitled to that country's citizenship at birth. They land in a country whose laws say anyone born on a flight landing in that country, regardless of its origin, is entitled to that country's citizenship at birth. Mom goes into labor and delivers the child while the plane is in U.S. air space (on its way to the destination country). The Immigration and Nationality Act interprets the 14th amendment to the U.S. Constitution as saying that, since the plane was within the jurisdiction of the United States and therefore subject to its laws, the child was effectively born on U.S. soil, and thus entitled to U.S. citizenship at birth. So already we're up to potentially 7 citizenships, just at birth.

What if mom and/or dad had even more citizenships that transmit? That child could start off with quite a collection. And then to naturalize in other countries throughout the global citizen's life, yes, potentially one individual could possess many different nationalities throughout one's life. Not probable, but definitely possible.

(Edited for typos.)

There is a scam going on in Italy. “Agents” are offering Italian citizenship for 30,000 Euros. They do it by showing that your grandfather was born in Italy. Some corrupt Italian officials are also involved who get “real” backdated birth certificate under you grandfather’s name.

I was referred to one such agent by someone who got Italian citizenship last year in the same way and is originally from India. A lot of Asians and Africans are doing it. You can only find the agents through word of mouth.

I declined the offer, even though I am desperate to get a citizenship of a developed country. I am scared if it may lead to some trouble in case this scandal comes out in the future.

Pretty much impossible.

Many countries require lengthy residency prior to granting nationalization, you will not live that long. Typically about 3 to 10 years. Some much longer, Oman for example is 30 years, several are in the 20 to 30 year range as well.

Many countries do not allow dual let alone multiple citizenships, you would have to renounce all other citizenships prior top taking that countries citizenship. The Philippines or Malaysia for example.

Most require you to speak the local language, or at least one of them, you would have to learn many languages as well. You may also have to adopt the local religion.

Some like China require that you be ethnic Chinese to even apply. The Vatican requires you to be a Cardinal in the Catholic church (There are only 450 citizens and 800 residents of the Vatican City) . It would be almost impossible to meet all the various requirements as some are contradictory, especially those dealing with ethnicity or religion.

See also

Naturalization - Wikipedia

and

8 of the countries where it's hardest to become a citizen