Some, but not all, of Turkey is in Europe. By the conventional definition, the part of Turkey that lies west of the Bosporus, the Sea of Marmara and the Dardanelles is in Europe, but the part of Turkey that lies to the east is in Asia.
The traditional land border between Europe and Asia runs along the Urals in Russia, to the Caspian Sea, and along the Caucasus Mountains from the Caspian Sea to the Black Sea. Most of Turkey lies south of the Black Sea, east of the straits connecting the Black Sea to the Mediterranean and is considered part of Asia. West of the strait is in Europe. Turkey, like Russia, straddles the border between Europe and Asia. Istanbul lies on both sides of the Bosporus and is also in both Europe and Asia.