Mamluk (Arabic: مملوك, romanized: mamlūk (singular), مماليك, mamālīk (plural); translated as "one who is owned", meaning "slave") is a term most commonly referring to White, non-Arab, ethnically diverse (mostly Turkic, Caucasian, Eastern and Southeastern European) enslaved mercenaries, slave-soldiers, and freed slaves who were assigned high-ranking military and administrative duties, serving the ruling Ottoman and Arab dynasties in the Muslim world.

The most enduring Mamluk realm was the knightly military class in medieval Egypt, which developed from the ranks of slave-soldiers. Originally the Mamluks were slaves of White Turkic origins from the Eurasian Steppe, but the institution of military slavery spread to include Circassians, Abkhazians, Georgians, Armenians, Russians, and Hungarians, as well as peoples from the Balkans such as Albanians, Greeks, and South Slavs (see Saqaliba). They also recruited from the Egyptians. The "Mamluk/­Ghulam Phe­nom­enon", as David Ayalon dubbed the creation of the specific warrior class, was of great political importance; for one thing, it endured for nearly 1,000 years, from the 9th to the 19th centuries.

Over time, Mamluks became a powerful military knightly class in various Muslim societies that were controlled by dynastic Arab rulers. Particularly in Egypt and Syria, but also in the Ottoman Empire, Levant, Mesopotamia, and India, mamluks held political and military power. In some cases, they attained the rank of sultan, while in others they held regional power as emirs or beys. Most notably, Mamluk factions seized the sultanate centered on Egypt and Syria, and controlled it as the Mamluk Sultanate (1250–1517). The Mamluk Sultanate famously defeated the Ilkhanate at the Battle of Ain Jalut. They had earlier fought the western European Christian Crusaders in 1154–1169 and 1213–1221, effectively driving them out of Egypt and the Levant. In 1302 the Mamluk Sultanate formally expelled the last Crusaders from the Levant, ending the era of the Crusades.

While Mamluks were purchased as property, their status was above ordinary slaves, who were not allowed to carry weapons or perform certain tasks. In places such as Egypt, from the Ayyubid dynasty to the time of Muhammad Ali of Egypt, mamluks were considered to be "true lords" and "true warriors", with social status above the general population in Egypt and the Levant. In a sense, they were like enslaved mercenaries.