The flag is called Ay Yildiz (Turkish for 'moon star'). Red is a prominent color in Turkish history, especially regarding the bloody battles of the Turkish War of Independence. The crescent and star, while generally regarded as Islamic symbols today, have for long been used in Asia Minor, quite before the advent of Islam. The flag was originally simply a crescent on a green field, but this was changed in 1793 when Sultan Selim III changed the background to red. In 1844, the star was added.

The most widely believed legend of the flag's origins tells of Mustafa Kemal Atatürk, the founder of the modern Turkish Republic, walking on a battlefield one night after a victorious battle in the Turkish War of Independence, and seeing the reflection of the star and crescent formation, in a large pool of blood on the rocky hill terrain of Sakarya.

Another theory regarding the flag dates it back to the Byzantine Empire. It states that a Crescent and Star were used as the symbol of the Greek city of Byzantion for centuries, and when the Ottomans took Constantinople, it was adopted as the symbol of the Ottoman Empire.