Troy (Hittite: Wilusa or Truwisa; Greek: Ἴλιον, Ilion, and Τροία, Troia; Latin: Trōia and Īlium; Turkish: Truva and Troia) was a city, both factual and legendary, located in northwest Anatolia in what is now Turkey, southeast of the Dardanelles and beside Mount Ida. It is best known for being the focus of the Trojan War described in the Greek Epic Cycle and especially in the Iliad, one of the two epic poems attributed to Homer. Metrical evidence from the Iliad and the Odyssey seems to show that the name Ἴλιον (Ilion) formerly began with a digamma: Ϝίλιον (Wilion). This was later supported by the Hittite form Wilusa.

A new city called Ilium was founded on the site in the reign of the Roman Emperor Augustus. It flourished until the establishment of Constantinople and declined gradually during the Byzantine era.

In 1865, English archaeologist Frank Calvert excavated trial trenches in a field he had bought from a local farmer at Hisarlık, and in 1868 Heinrich Schliemann, wealthy German businessman and archaeologist, also began excavating in the area after a chance meeting with Calvert in Çanakkale. These excavations revealed several cities built in succession. Troy VII has been identified with the Hittite Wilusa, the probable origin of the Greek Ἴλιον, and is generally (but not conclusively) identified with Homeric Troy.

Today, Truva is a small Turkish city supporting the tourist trade visiting the Troia archaeological site. Troia was added to the UNESCO World Heritage list in 1998.

Ancient Greek historians placed the Trojan War variously in our 12th, 13th, or 14th century BC: Eratosthenes to 1184 BC, Herodotus to 1250 BC, Duris of Samos to 1334 BC. Modern archaeologists associate Homeric Troy with archaeological Troy VII.

In the Iliad, the Achaeans set up their camp near the mouth of the river Scamander (presumably modern Karamenderes), where they had beached their ships. The city of Troy itself stood on a hill, across the plain of Scamander, where the battles of the Trojan War took place. The site of the ancient city is some 5 km from the coast today, but the ancient mouths of alleged Scamander, some 3,000 years ago, were about that distance inland, pouring into a large bay which formed a natural harbour, but has since been filled with alluvial material. Recent geological findings have permitted the reconstruction of how the original Trojan coastline would have looked, and the results largely confirm the accuracy of the Homeric geography of Troy.

Besides the Iliad, there are references to Troy in the other major work attributed to Homer, the Odyssey, as well as in other ancient Greek literature. The Homeric legend of Troy was elaborated by the Roman poet Virgil in his Aeneid. The Greeks and Romans took for a fact the historicity of the Trojan War and the identity of Homeric Troy with the site in Anatolia. Alexander the Great, for example, visited the site in 334 BC and made sacrifices at tombs there associated with the Homeric heroes Achilles and Patroclus.

In November 2001, geologists John C. Kraft from the University of Delaware and John V. Luce from Trinity College, Dublin presented the results of investigations, begun in 1977, into the geology of the region. They compared the present geology with the landscapes and coastal features described in the Iliad and other classical sources, notably Strabo's Geographia, and concluded that there is a regular consistency between the location of Schliemann's Troy and other locations such as the Greek camp, the geological evidence, descriptions of the topography and accounts of the battle in the Iliad. Further work by John Kraft and others was published in 2003.

After the 1995 find of a Luwian biconvex seal at Troy VII, there has been a heated discussion over the language that was spoken in Homeric Troy. Frank Starke of the University of Tübingen recently demonstrated that the name of Priam is connected to the Luwian compound Priimuua, which means 'exceptionally courageous'. "The certainty is growing that Wilusa/Troy belonged to the greater Luwian-speaking community", although it is not entirely clear whether Luwian was primarily the official language or in daily colloquial use.

The layers of ruins in the citadel at Hisarlik are numbered Troy I – Troy IX, with various subdivisions: