Istanbul

Istanbul is Turkey’s largest city and a megacity that serves as the nation’s economic, cultural, and historical hub. Its population exceeds 15 million, accounting for 18% of Turkey’s total residents, placing it among the most populous cities in both Europe and the world. The city spans two continents: roughly two-thirds of its inhabitants live on the European side, with the remainder on the Asian side. It sits astride the Bosphorus—one of the globe’s busiest waterways—in northwestern Turkey, positioned between the Sea of Marmara and the Black Sea. Covering 5,461 square kilometers, its boundaries match those of Istanbul Province.

The settlement grew into one of history’s most important cities. Greek colonists founded Byzantium on the Sarayburnu promontory in the seventh century BC. After being reestablished as Constantinople in 330 AD, it served as the capital of four empires over nearly 1,600 years: the Roman Empire (330–395), the Eastern Roman (Byzantine) Empire (395–1204 and 1261–1453), the Latin Empire (1204–1261), and the Ottoman Empire (1453–1922). During Roman and Byzantine times, it played a key role in advancing Christianity, but after the Ottoman conquest in 1453, it became an Islamic stronghold and the seat of the caliphate. Although the Republic of Turkey moved its capital to Ankara, Istanbul’s hills remain lined with palaces and imperial mosques that recall its former centrality. Its historic center is a UNESCO World Heritage Site.

Istanbul’s strategic location along the historic Silk Road, its rail links to Europe and West Asia, and its position as the only sea route between the Black Sea and the Mediterranean have long fostered a diverse population—though this diversity has lessened since the Republic’s founding in 1923. Passed over for the new capital during the interwar period, the city has since regained much of its importance. Since the 1950s, its population has increased tenfold as migrants from across Anatolia have arrived, and city limits have expanded to accommodate them. Most of Istanbul’s Turkish citizens are of ethnic Turkish origin, while ethnic Kurds form the largest minority.

Classified as an alpha global city, Istanbul generates about 30% of Turkey’s economy. The Istanbul-İzmit area is one of the country’s main industrial regions. In 2025, Euromonitor International ranked it the fifth most visited city worldwide. It has two international airports, multiple ports, and numerous universities, and it ranks among the top 100 science and technology clusters globally. The city hosts a large share of Turkish football and sports, with clubs like Galatasaray, Fenerbahçe, and Beşiktaş. Istanbul is vulnerable to earthquakes due to its proximity to the North Anatolian Fault.

Names The city’s first known name is Byzantium, given by Megarian colonists around 657 BC. They claimed descent from Byzas, son of the god Poseidon and the nymph Ceroëssa. Modern excavations suggest the name may reflect earlier Thracian settlements on the site. Constantinople comes from the Latin name for Constantine the Great, the Roman emperor who refounded the city in 324 AD.

He initially called it New Rome. Constantinople remained the most common Western name until the 1930s, when Turkish authorities urged foreign languages to use Istanbul. The Ottomans alternately used Kostantiniyye and İstanbul. The name İstanbul likely derives from the Medieval Greek phrase eis tin polin (“to the city”), reflecting its status as the only major city nearby.

Its Ottoman nickname Der Saadet meant “Gate to Prosperity.” An alternative view is that the name evolved directly from “Constantinople” by dropping the first and third syllables. Seventeenth-century Ottoman sources like Evliya Çelebi describe it as the common Turkish name; between the late 17th and late 18th centuries, it was also official. The first use of İstanbul on coinage was in 1730 under Sultan Mahmud I. In modern Turkish, it is written İstanbul with a dotted İ.

In English, stress falls on the first or last syllable; in Turkish, on the second. A person from the city is an İstanbullu (plural İstanbullular); Istanbulite is used in English.

History Neolithic artifacts from the early 21st century show that Istanbul’s historic peninsula was settled as early as the 6th millennium BC. This settlement, important for spreading the Neolithic Revolution from the Near East to Europe, lasted nearly a millennium before rising waters submerged it. On the Asian side, the Fikirtepe mound dates from the Copper Age (5500–3500 BC). On the European side, near Sarayburnu, a Thracian settlement existed in the early 1st millennium BC.

Modern authors link it to the Thracian toponym Lygos, mentioned by Pliny the Elder as an earlier name for Byzantium’s site. The city’s proper history begins around 660 BC, when Greek settlers from Megara established Byzantium on the European side of the Bosporus. They built an acropolis near the Golden Horn on earlier Thracian settlements, boosting the young city’s economy. It briefly fell under Persian rule at the turn of the 5th century BC.