Cities end up with more than one name for three main reasons. Foreigners pass down their own forms of a name (exonyms such as Danzig for Gdańsk). Rulers rename cities to mark a change of regime (Saint Petersburg became Petrograd, then Leningrad, then Saint Petersburg again). And writing systems change how a name is spelled in another alphabet (Peking became Beijing). Istanbul, also known as Byzantium and Constantinople, Mumbai (Bombay), Kolkata (Calcutta), Chennai (Madras), Kyiv (Kiev) and Ho Chi Minh City (Saigon) each show at least one of these at work. The cases below test each explanation against the record. In most of them more than one is true, and the most familiar story about the name is often wrong.
Three rival explanations: outsiders' names, rulers' names or spelling systems
The first explanation is linguistic. The Australian geographer Marcel Aurousseau coined the word "exonym" in The Rendering of Geographical Names (1957), and the United Nations Group of Experts on Geographical Names (UNGEGN) later defined the pair. An endonym is the name used in the language of the place itself. An exonym is a name used in another language that differs from it in form. Wien is the endonym and Vienna the English exonym. Seen this way, a city has many names because many languages talk about it, and none of those names has to be political.
The second explanation is political: a city's names follow the regimes that held it, so each name records a conquest, a revolution or a dedication. The third is technical. Many apparent second names are not names at all, only different ways of writing the same word in the Latin alphabet, and they change when a romanisation system changes. Each theory predicts something different. If the first is right, the competing forms should be old and should come from neighbours' languages. If the second is right, the changes should come on dates set by governments. If the third is right, the "old" and "new" names should be the same word in the original script.
The exonym case: Gdańsk, Danzig and the drift of one word since 997
Gdańsk on the Baltic is the clearest case for the first theory, because its two names turn out to be one word. The earliest record is the first biography of St Adalbert of Prague, written after his death in 997. It says that in that year he baptised the people of urbs Gyddanyzc. Later documents give Kdanzk (1148), Gdanzc (1188), Danceke (1228), Gdańsk (1236), Danzc (1263), Danczik (1399) and Danczig (1414). The German Danzig and the Polish Gdańsk grew out of the same medieval word as German speakers and Polish speakers each said it their own way. The Latin forms Gedania and Dantiscum come from the same source.
The politics came later. The city was annexed by Prussia in 1793, was a free city from 1807 to 1814 and again from 1920 to 1939, and after 1945 its German population fled or was expelled. Only then did choosing between Danzig and Gdańsk become a political statement. So the evidence supports the linguistic theory for where the two names came from, and the political theory for why the choice later mattered.
The romanisation case: Pequim, Peking and pinyin's Beijing
Beijing fits the third theory almost exactly. In Chinese the name 北京, "Northern Capital", dates from 1403, when the Ming Yongle Emperor gave his northern base that title to pair it with Nanjing, the "Southern Capital". The Portuguese wrote it Pequim, a form found in letters by Francis Xavier in 1552. The Jesuit Martino Martini used "Peking" in his Novus Atlas Sinensis of 1655, and the Imperial Post Office settled on Peking in the 1890s. China approved Hanyu Pinyin in 1958 and pushed it abroad from 1979. The New York Times switched to "Beijing" in November 1986, the Associated Press and United Press International on 1 March 1987, and the BBC in 1990. The characters 北京 did not change in that switch.
The city did also have real political renamings, which makes it a mixed case. The Republic of China moved its capital to Nanjing and renamed the city Beiping (北平, "Northern Peace") in 1928. Japan restored Peking during its occupation in 1938, Beiping returned in 1945, and the People's Republic brought back Beijing in 1949. Even so, the change most English speakers know, from Peking to Beijing, was only a change of spelling. "Peking" survives in Peking University and Peking duck.
Kyiv sits between the second and third theories. Kiev and Kyiv are romanisations of the Russian Киев and the Ukrainian Київ. Ukraine made Kyiv the legal spelling in 1995. The UN conference on standardising geographical names accepted it in 2012, and Ukraine's foreign ministry began its #KyivNotKiev campaign on 2 October 2018. The US Board on Geographic Names adopted Kyiv in June 2019, and IATA followed in October 2019. On paper this is a spelling question, but in practice the choice of spelling is political. The name itself has rival etymologies too. The Primary Chronicle derives it from Kyi, a legendary founder, an account the historian Mykhailo Hrushevsky called an "etymological myth". The linguist Jaroslav Rudnyckyj read it instead as a "palisaded settlement".
The renaming case: Sankt-Peterburg, Petrograd, Leningrad and back
Saint Petersburg is the strongest case for the political theory, because every change of name since its founding came on a known date for a stated reason. Peter the Great founded the city on 27 May 1703 and named it after the apostle Peter. On 31 August 1914 (18 August in the old calendar), weeks into the war with Germany, Nicholas II renamed it Petrograd to remove the German words Sankt and Burg. Dropping "Saint" also quietly changed whom the name honoured, from the apostle to Peter the Great. On 26 January 1924, days after Lenin died, it became Leningrad. In a city referendum on 12 June 1991, 55% voted for Saint Petersburg and 43% for Leningrad, and the old name returned on 6 September 1991. The region around the city is still called Leningrad Oblast, and residents often just say Piter.
Volgograd is a similar case. As Tsaritsyn it became Stalingrad in 1925, and it was renamed Volgograd in 1961. Ho Chi Minh City also fits the political theory, but less neatly. After reunification in 1976 Saigon was renamed after the North Vietnamese leader. "Saigon" itself is probably a Vietnamese rendering of an older Khmer name, Prey Nokôr. It is still used informally, and since 2025 it has been the official name of the city's administrative centre.
Mumbai, Kolkata and Chennai: when the colonial-name theory meets the evidence
India's renamings in 1995, 1996 and 2001 are usually described as getting rid of colonial names. The evidence for each city is less simple. Bombay became Mumbai officially in November 1995, at the insistence of the Shiv Sena, which had just won the Maharashtra state election and argued that "Bombay" recalled British rule. Mumbai comes from Mumbā, the goddess Mumbadevi of the Koli fishing community, with ā'ī, Marathi for "mother". The colonial form has its own folk etymology: some English-language writers suggested that a supposed Portuguese phrase bom baim, "good little bay", lay behind Bombaim and Bombay, a claim with no scientific basis. Back in 1877 the French traveller Louis Rousselet wrote that etymologists had wrongly derived the name from "Bôa Bahia", and the British officer John Briggs called Bombay a corruption of "Mumby". On this evidence Bombay was a foreign rendering of a local name, not a foreign coinage.
Chennai goes further against the colonial reading. Tamil Nadu replaced Madras with Chennai in July 1996, but Madras was not British either. A Vijayanagara-era inscription found in 2015 and dated to 1367 mentions a port called Mādarasanpattanam, long before the East India Company arrived. Chennai comes from Chennappa Nayaka, a general under the Vijayanagara Empire, and its first official use was in a sale deed of August 1639 to Francis Day of the East India Company. Both names are Indian in origin. The renaming chose one local name over another. Kolkata, renamed in 2001, shows the third theory at work. Calcutta was only an English spelling of the Bengali Kôlikata, one of three villages, with Sutanuti and Govindapur, that existed before the British arrived. The meaning of Kôlikata is still disputed. Proposals include Kalikshetra, "field of Kali", the nearby Kalighat, khal plus kata ("dug canal"), and the local trade in quicklime and coir.
Istanbul: every theory at once, from Byzantion to the 1930 request
Istanbul is the case where all three explanations hold together. Pliny the Elder recorded an earliest name, Lygos, whose meaning is unknown. Greek colonists from Megara founded Byzantion in the 7th century BC (667 BC in one dating, about 660 BC in others). Its name is thought to be Thracian or Illyrian, perhaps from a personal name Byzas, whom legend made the founder. Septimius Severus briefly called it Augusta Antonina after his son. Constantine dedicated it as his capital on 11 May 330, and Constantinople became its official name, attested under Theodosius II, while the First Council of Constantinople in 381 also called it New Rome. Those are political names, in the second theory's sense. The term "Byzantium" for the whole empire came much later, from the historian Hieronymus Wolf in 1555.
İstanbul itself supports the linguistic theory. It appears in Arabic and Armenian sources from the 10th century, centuries before the Ottoman conquest of 1453. It is usually traced to the Greek eis tin polin, "to the city". A 2015 review of the literature cited on Wikipedia prefers the spoken Middle Greek stin Poli(n), probably meaning "in Constantinople". Islambol, "full of Islam", first attested shortly after the conquest, was an Ottoman play on the name and not its source. The Ottomans kept Kostantiniyye in chancery formulae, and used it on coins until the late 17th century and again in the 19th. The third theory covers the last step. After Turkey switched to the Latin alphabet in 1928, it asked other countries from 1930 to use Turkish forms of Turkish place names, and the US State Department adopted "Istanbul" in May 1930.
More on the city's names is in our guide to the origin of the name Istanbul. Beijing's "Northern Capital" story is told in full in where the name Beijing comes from. For the same reasoning applied to whole nations, see exonyms and endonyms for country names.