Ibrahim I (Ottoman Turkish: ابراهيم اول) (November 5, 1615 – August 12/18, 1648) was the Sultan of the Ottoman Empire from 1640 until 1648. He was born in Istanbul the son of Ahmed I by Valide Sultan Kadinefendi Kösem Sultan, an ethnic Greek originally named Anastasia.

One of the most famous Ottoman Sultans, he was released from the Kafes and succeeded his brother Murad IV (1623 – 40) in 1640, though against the wishes of Murad IV, who had ordered him killed upon his own death. Murad IV had himself succeeded their older brother Osman II in 1622, and had ordered his three other brothers executed.

Ibrahim at first stayed away from politics, but eventually he took to raising and executing a number of viziers. A war with Venice was fought, and in spite of the decline of La Serenissima, Venetian ships won victories throughout the Aegean, capturing Tenedos (1646), the gateway to the Dardanelles. Ibrahim's rule grew ever more unpredictable. Eventually, he was deposed in a coup led by the Sheikh ul-Islam. There is an apocryphal story to the effect that the Sheikh ul-Islam acted in response to Ibrahim's decision to drown all 280 members of his harem, but there is other evidence to suggest that at least two of Ibrahim's concubines survived him (particularly Turhan Hatice, who was responsible for the death three years later of Kösem, then serving as regent for Ibrahim's son by Hatice, Mehmed IV). Chances are this story was circulated after the coup to silence those who for whatever reason preferred a mad sultan. He was strangled in Istanbul at the behest of the Grand Vizier Mevlevî Mehmed Paşa (Sofu Mehmed Pasha).

He was married to Turhan Hatice (Khadija) Valide Sultan, a Ukrainian (the mother of Mehmed IV), to Saliha Dilâşub Valide Sultan (the mother of Suleiman II), and to Hatice (Khadija) Muazzez Sultan (the mother of Ahmed II).