By the end of the 13th century the Anatolian Seljuk state had fractured under Mongol pressure. Into this vacuum rose dozens of independent Turkmen beyliks. In the Söğüt region, a small frontier beylik facing the Byzantine border — the Kayı tribe under Osman Bey — expanded with unusual energy. Tradition dates the founding moment to Osman's emergence as an independent ruler around 1299, but there is no single founding event: it was a process spread over years.

In its first decades the Ottoman state captured key Byzantine cities including Bursa (1326) and İznik (1331). By the mid-14th century Ottoman forces had crossed into the Balkans; Edirne fell in 1369. The 15th century saw further advance into Europe, culminating in Mehmed II's conquest of Constantinople in 1453 and the end of Byzantium. In the 16th century Selim I defeated the Mamluks and Suleiman raised the empire to its widest reach across Europe, Asia, and Africa.

The Ottoman Empire developed a complex apparatus for governing many faiths and peoples: the millet system, the devshirme, and the triangle of palace, ulema, and military. Its classical peak came in the mid-16th century; afterwards began a long structural transformation. The state collapsed in the aftermath of the First World War, and the nation-states that emerged from it — above all the Republic of Turkey — shaped much of today's Mediterranean, Balkans, and Middle East.