Bayezid I (Ottoman: بايزيد اول, Turkish: Beyazıt, nicknamed Yıldırım (Ottoman: ییلدیرم), "the Thunderbolt", Serbian: Бајазит / Bajazit; 1360, Bursa – March 8, 1403, Akşehir, Turkey) was the Sultan of the Ottoman Empire, then Rûm, from 1389 to 1402. He was the son of Murad I and Valide Sultan Gülçiçek Hatun who was of ethnic Greek descent.
Bayezid ascended to the throne following the death of his father Murad I, who was killed by Serbian nobleman Miloš Obilić during (June 28), or immediately after (June 29), the Battle of Kosovo in 1389. With this battle, Serbia had become a vassal of the Ottoman Empire. A year later, Bayezid took as a wife Princess Olivera Despina, the daughter of Prince Lazar of Serbia, who also lost his life in Kosovo. Bayezid recognized Stefan Lazarević, the son of Lazar, as the new Serbian leader (later despot), with considerable autonomy.