İzmir is the third most populous city in Turkey, after Istanbul and Ankara. It is on the Aegean coast of Anatolia, and is the capital of İzmir Province. As of 2024, İzmir Province has a total population of 4,493,242 while İzmir city is home to around 3.3 million inhabitants. It extends along the outlying waters of the Gulf of İzmir and inland to the north across the Gediz River Delta; to the east along an alluvial plain created by several small streams; and to slightly more rugged terrain in the south. İzmir's climate is Mediterranean.

İzmir has more than 3,000 years of recorded urban history, and up to 8,500 years of history as a human settlement since the Neolithic period. In classical antiquity, the city was known as Smyrna – a name which remained in use in English and various other languages until around 1930, when government efforts led the original Greek name to be gradually phased out internationally in favor of its Turkish counterpart İzmir.

Lying on an advantageous location at the head of a gulf running down in a deep indentation, midway along the western Anatolian coast, İzmir has been one of the principal mercantile cities of the Mediterranean Sea for much of its history. Until the 1923 population exchange between Greece and Turkey, İzmir had a very large Greek population. Present-day İzmir is an important port, and is home to multiple universities. It hosts the annual İzmir International Fair.

In ancient Anatolia, the name of a locality called Ti-smurna is mentioned in some of the Level II tablets from the Assyrian colony in Kültepe (first half of the 2nd millennium BC), with the prefix ti- identifying a proper name, although it is not established with certainty that this name refers to modern-day İzmir.

The modern name İzmir is the Turkish rendering of the Greek name Smyrna (/ˈsmɜːrnə/ SMUR-nə; Greek: Σμύρνη, romanized: Smýrni/Smýrnē). In medieval times, Westerners used forms like Smire, Zmirra, Esmira, Ismira, which was rendered as İzmir into Turkish, originally written as ازمير with the Ottoman Turkish alphabet.

The region of İzmir was situated on the southern fringes of the Yortan culture in Anatolia's prehistory, knowledge of which is almost entirely drawn from its cemeteries. In the second half of the 2nd millennium BC, it was in the western end of the extension of the still largely obscure Arzawa Kingdom, an offshoot and usually a dependency of the Hittites, who themselves spread their direct rule as far as the coast during their Great Kingdom. That the realm of the 13th century BC local Luwian ruler, who is depicted in the Kemalpaşa Karabel rock carving at a distance of only 50 km (31 mi) from İzmir was called the Kingdom of Myra may also leave grounds for association with the city's name.

The latest known rendering in Greek of the city's name is the Aeolic Greek Μύρρα Mýrrha, corresponding to the later Ionian and Attic Σμύρνα (Smýrna) or Σμύρνη (Smýrnē), both presumably descendants of a Proto-Greek form *Smúrnā. Some would see in the city's name a reference to the name of an Amazon called Smyrna said to have seduced Theseus, leading him to name the city in her honor. Others link the name to the Myrrha commifera shrub, a plant producing the aromatic resin called myrrh that is indigenous to the Middle East and northeastern Africa, which was the city's chief export in antiquity. The Romans took over this name as Smyrna, which is still the name used in English when referring to the city in pre-Turkish times. In Ottoman Turkish the town's name was ازمير Izmīr.^{[citation needed]}

In English, the city was called Smyrna into the 20th century. Izmir (sometimes İzmir) was adopted in English and most foreign languages after Turkey adopted the Latin alphabet in 1928 and urged other countries to use the city's Turkish name. However, the historic name Smyrna is still used today in some languages, such as Italian (Smirne), and Catalan, Portuguese, and Spanish (Esmirna).