Assyrians in Turkey (Turkish: Türkiye Süryanileri, Syriac: ܣܘܪܝܝܐ ܕܛܘܪܩܝܐ) or Turkish Assyrians are the indigenous Semitic-speaking ethnic group and an oppressed minority of Turkey, who are Eastern Aramaic–speaking Christians, with most being members of the Syriac Orthodox Church, Chaldean Catholic Church, Assyrian Pentecostal Church, Assyrian Evangelical Church, or Ancient Church of the East.

They share a common history and ethnic identity, rooted in shared linguistic, cultural and religious traditions, with Assyrians in Iraq, Assyrians in Iran and Assyrians in Syria, as well as with the Assyrian diaspora. Assyrians in such European countries as Sweden and Germany would usually be Turoyo-speakers or Western Assyrians, and tend to be originally from Turkey.

The Assyrians were once a large ethnic minority in the Ottoman Empire, living in the Hakkari, Sirnak and Mardin provinces, but, following the Sayfo (1915, also known as the Assyrian genocide), most were murdered or expelled to northern Iraq, northeast Syria, and northwest Iran, to join their fellow Assyrians. Most of those who survived the genocide and stayed in Turkey left the country for Western Europe in the 2nd half of the 20th century, due to conflicts between the Kurdistan Workers' Party (PKK) and the Turkish Land Forces. As of 2019, an estimated 18,000 of the country's 25,000 Assyrians live in Istanbul. According to Yusuf Çetin, Spiritual Leader of the Syriac Orthodox Community, as of 2023, there are 25,000-30,000 Assyrians in Turkey, including 17,000 to 22,000 in Istanbul, most of them in Yeşilköy, where the new Mor Ephrem Syriac Orthodox Church was inaugurated on 8 October 2023.

The Ottoman Empire had an elaborate system of administering the non-Muslim "People of the Book." That is, they made allowances for accepted monotheists with a scriptural tradition and distinguished them from people they defined as pagans. As People of the Book (or dhimmi), Jews, Christians and Mandaeans (in some cases Zoroastrians) received second-class treatment but were tolerated.

In the Ottoman Empire, this religious status became systematized as the "millet" administrative pattern. Each religious minority answered to the government through its chief religious representative. The Christians that the Ottomans conquered gradually but definitively with the conquest of Constantinople in 1453 were already divided into many ethnic groups and denominations, usually organized into a hierarchy of bishops headed by a patriarch.

As for the 5 Assyrian Tribes of Hakkari, The Shimun Patriarchate in Qodshanis, who the Tribes worshipped because it was the Assyrian Church of the East's Holy See: was directly subservient to the Sublime Porte, who the see paid the taxes to which they collected from the tribes.

Those who had converted to Protestantism did not want to pay an annual tribute to the older churches through local bishops who then passed some of it up to the Patriarch who then passed some of it to the Porte in the form of taxes. They wanted to deal directly with the Porte, across ethnic lines (even if through a Muslim administrator), in order to have their own voice and not be subjected to the rule of the Patriarchal system. This general Protestant charter was granted in 1850.

During the Second Bedirkhanis Revolt, a Kurdish revolt which erupted during the Russo-Turkish War of 1877 to 1878, the Syriac-Assyrians under the leadership of Hanne Safar provided significant military support to the Ottoman Empire. For his assistance and loyalty throughout the revolt, Hanne Safar was later honored by the Sultan himself, Abdülhamid II, with the title of Pasha and was presented with a consecrated sword. Despite the region around Midyat avoiding the Hamidian massacres, Assyrians of other areas such as Diyarbakir were less fortunate, which resulted in the death of approximately 25,000 Assyrians during the Massacres of Diyarbakir in 1895.