Hayreddin Barbarossa, also known as Hızır Hayrettin Pasha, and simply Hızır Reis, was an Ottoman corsair and later admiral of the Ottoman Navy. Barbarossa's naval victories secured Ottoman dominance over the Mediterranean during the mid 16th century.

Hayreddin Barbarossa (Arabic: خير الدين بربروس‎, romanized: Khayr al-Din Barbarus, original name Khiḍr; Turkish: Barbaros Hayrettin Paşa), also known as Hızır Hayrettin Pasha, and simply Hızır Reis (c. 1466/1478 – 4 July 1546), was an Ottoman corsair and later admiral of the Ottoman Navy.Barbarossa's naval victories secured Ottoman dominance over the Mediterranean during the mid 16th century.

Born on Lesbos, Khizr began his naval career as a corsair under his elder brother Oruç Reis. In 1516, the brothers captured Algiers from Spain, with Oruç declaring himself as Sultan. Following Oruç's death in 1518, Khizr inherited his brother's nickname, "Barbarossa" ("Redbeard" in Italian). He also received the honorary name Hayreddin (from Arabic Khayr ad-Din, "goodness of the faith" or "best of the faith"). In 1529, Barbarossa retook the Peñón of Algiers from the Spaniards.

In 1533, Barbarossa was appointed Kapudan Pasha (Grand admiral) of the Ottoman Navy by Suleiman the Magnificent. He led an embassy to France in the same year, conquered Tunis in 1534, achieved a decisive victory over the Holy League at Preveza in 1538, and conducted joint campaigns with the French in the 1540s. Barbarossa retired to Constantinople in 1545 and died the following year.