Abdulmejid I (Ottoman Turkish: عبد المجيد اول, romanized: ʿAbdü'l-Mecîd-i evvel, Turkish: I. Abdülmecid; 25 April 1823 – 25 June 1861) was the 31st sultan of the Ottoman Empire and succeeded his father Mahmud II on 2 July 1839. His reign was notable for the rise of nationalist movements within the empire's territories. Abdulmejid wanted to encourage Ottomanism among secessionist subject nations and stop rising nationalist movements within the empire, but despite new laws and reforms to integrate non-Muslims and non-Turks more thoroughly into Ottoman society, his efforts failed in this regard.

He tried to forge alliances with the major powers of Western Europe, namely the United Kingdom and France, who fought alongside the Ottoman Empire in the Crimean War against Russia. During the Congress of Paris on 30 March 1856, the Ottoman Empire was officially included among the European family of nations.

Abdulmejid's biggest achievement was the announcement and application of the Tanzimat (reorganization) reforms which were prepared by his father and effectively started the modernization of the Ottoman Empire in 1839. For this achievement, one of the imperial anthems of the Ottoman Empire, the March of Abdulmejid, was named after him.