thumb|304x304px|Illustration of an Ottoman official and his assistant registering Christian boys for the devshirme. The official takes a tax to cover the price of the boys' new red clothes and the cost of transport from their home, while the assistant records their village, district and province, parentage, date of birth and physical appearance. Ottoman miniature painting, 1558.
Devshirme (, usually translated as "child levy" or "blood tax") was the Ottoman practice of forcibly recruiting soldiers and bureaucrats from among the children of their Balkan Christian subjects and raising them in the religion of Islam. Those coming from the Balkans came primarily from noble Balkan families and rayah classes. It is first mentioned in written records in 1438, It counterbalanced the Turkish nobility, who sometimes opposed the Sultan.
The system produced a considerable number of grand viziers from the 15th century to the 17th century. This was the second most powerful position in the Ottoman Empire, after the sultan. Initially, the grand viziers were exclusively of Turk origin, but after there were troubles between Sultan Mehmed II and the Turkish grand vizier Çandarlı Halil Pasha the Younger, who was the first grand vizier to be executed, there was a rise of slave administrators (devshirme). They were much easier for the sultans to control, compared to free administrators of Turkish aristocratic extraction. The devshirme also produced many of the Ottoman Empire's provincial governors, military commanders, and divans from the 15th to the 17th century. Sometimes, the devshirme recruits were castrated and became eunuchs. Although often destined for the harem, many eunuchs of devshirme origin went on to hold important positions in the military and the government, such as grand viziers Hadım Ali Pasha, Sinan Borovinić, and Hadım Hasan Pasha.
Ottoman officials would take male Christian children, aged 7 to 20, from Eastern, Southern and Southeastern Europe, and relocate them to Istanbul, where they were converted, circumcised, assimilated and trained to serve in the Janissary infantry corps or for palace duties. Devshirme were rarely sold, though some could end up as slaves in private households. However, revolts were rare, with the exception of a revolt against the devshirme in Albania in 1565. Ordered to cut all ties with their families, some managed to use their positions to help their families. Muslims were not allowed into the system (with some exceptions), but some Muslim families smuggled their sons in anyway. According to Speros Vryonis, "The Ottomans took advantage of the general Christian fear of losing their children and used offers of devshirme exemption in negotiations for surrender of Christian lands. Such exemptions were included in the surrender terms granted to Jannina, Galata, Morea, Chios, etc. Christians who engaged in specialized activities important to the Ottoman state were exempted from the devshirme on their children by way of recognition of the importance of their labors for the empire. Exemption from this tribute was considered a privilege and not a penalty."
Many scholars consider the practice of devshirme as violating Islamic law. David Nicolle writes that enslavement of Christian boys violates the dhimmi protections guaranteed in Islam, but Halil İnalcık argues that the devshirme were not slaves once converted to Islam.