Ghilman (singular Arabic: غُلاَم ghulām, plural غِلْمَان ghilmān) were slave-soldiers and/or mercenaries in armies throughout the Islamic world. Islamic states from the early 9th century to the early 19th century consistently deployed slaves as soldiers, a phenomenon that was very rare outside of the Islamic world.

The Quran mentions ghilman (غِلْمَان) as eternal Male youths who are one of the delights of Jannah or paradise/heaven of Islam, in verse 52:24 (Verse 56:17 is also thought to refer to ghilman).

The words ghilman (غِلْمَان) and its singular variant ghulam (غلام) are of Arabic origin, meaning boys or servants. It derives from the Arabic root ḡ-l-m (غ ل م).

The ghilman were slave-soldiers taken as prisoners of war from conquered regions or frontier zones, especially from among the Turkic people of Central Asia and the Caucasian peoples (Turkish: Kölemen). They fought in bands, and demanded high pay for their services.

The idea of slave soldiers is sometimes projected back to the earliest Islamic period, but there is no evidence that the Prophet Muhammad or the Rashidun Caliphs organized slave armies. While individuals of slave origin, such as freedmen or war captives, may have joined battles voluntarily, the systematic use of slave soldiers did not exist at that time. Under the Umayyads, some Slavs and Berbers were employed in military roles, but it was only by the mid-9th century, particularly under the Abbasids, that the large-scale recruitment of slave soldiers, such as the ghilman, became a defining feature of Islamic military systems. The first Muslim ruler to form an army of slave soldiers, before the Abbasid Caliphs, seems to have been Ibrahim I ibn al-Aghlab (800–812), founder of the Aghlabids of Ifriqiya, where there was already a large population of agricultural slaves and access to extensive slave trading networks across the Sahara Desert.

Ghilman were introduced to the Abbasid Caliphate during the reign of al-Mu'tasim (r. 833–842), who showed them great favor and relied upon them for his personal guard. Accounts cite that their numbers increased in the caliphal household as Mu'tasim tried to address the court factionalism. These slave-soldiers were opposed by the native Arab population, and riots against them in Baghdad in 836 forced Mu'tasim to relocate his capital to Samarra.

The use of ghilman reached its maturity under al-Mu'tadid and their training was conceived and inspired through the noble furusiyya. From a slave, a ghulam attained his freedom after completing the formative training period and joined the elite corps as a mounted warrior. The ghilman rose rapidly in power and influence, and under the weak rulers that followed Mu'tasim, they became kingmakers: they revolted several times during the so-called "Anarchy at Samarra" in the 860s and killed four caliphs. Eventually, starting with Ahmad ibn Tulun in Egypt, some of them became autonomous rulers and established dynasties of their own, leading to the dissolution of the Abbasid Caliphate by the mid-10th century.

In Umayyad Spain, slave soldiers of "saqaliba" (Slavs) were used from the time of Al-Hakam I, but only became a large professional force in the tenth century, when the slave soldier recruitment shifted to Christian Spain, particularly the Kingdom of León.