The Directorate of Religious Affairs in Turkey (Turkish: Diyanet İşleri Başkanlığı, normally referred to simply as the Diyanet) is an official state institution established in 1924 by the orders of Mustafa Kemal Atatürk under article 136 of the Constitution of Turkey to carry out some of the administrative duties previously managed by the Shaykh al-Islām, before the abolition of the Ottoman Caliphate. The President of the Directorate of Religious Affairs is considered the Grand Mufti of Turkey.

As specified by law, the duties of the Diyanet are “to administrate the affairs related to faith and worship of the religion of Islam”. The Diyanet drafts a weekly sermon delivered at the nation's 85,000 mosques and more than 2,000 mosques abroad that function under the directorate. It provides Quranic education for children and trains and employs all of Turkey's imams, who are considered civil servants.

Starting from 2006, the Diyanet was fortified, by 2015 its budget had increased four-fold, and staff doubled to nearly 150,000. Its 2019 budget has been estimated at €1.7 billion ($1.87 billion), far exceeding that of most Turkish government ministries. It has 1,000 branches across Turkey and offers educational, cultural, and charitable activities in 145 countries.Diyanet TV was launched in 2012, now broadcasting 24 hours a day. It has expanded Quranic education to early ages and boarding schools – "enabling the full immersion of young children in a religious lifestyle" – and now issues fatwa (Turkish: fetva) on demand.