Abdul Mejid I (Ottoman Turkish: عبد المجید اول, romanized: ʿAbdü'l-Mecîd, Turkish: I. Abdülmecid; 25 April 1823 – 25 June 1861) was the 31st sultan of the Ottoman Empire. He succeeded his father Mahmud II on 2 July 1839.

Abdulmejid's greatest achievement was the announcement of the Tanzimat Edict upon his accession, prepared by his then Foreign Minister Mustafa Reshid Pasha, which effectively began the Tanzimat era, or era of reorganization, in the Ottoman Empire. He was a mild-mannered monarch, giving the Sublime Porte the autonomy needed for its reform projects. One of the main goals of the Tanzimat was to encourage Ottomanism among the millets to 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, in the long term, the movement failed.

Abdulmejid forged alliances with the major powers of Western Europe, namely the United Kingdom and France, which 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 Concert of Europe. Abdulmejid suddenly died of tuberculosis and was succeeded by his half-brother, Abdul Aziz.

Abdülmecid was born on 25 April 1823 at Beşiktaş Palace or at Topkapı Palace, in Istanbul. His mother was the Georgian consort Bezmiâlem Kadın.

Abdülmecid received a European education and was the first sultan to speak fluent French. Like Abdülaziz who succeeded him, he was interested in literature and classical music.

When Abdülmecid acceded to the throne on 2 July 1839, he was only sixteen and inexperienced, and the affairs of the Ottoman Empire were in a critical state. His father Mahmud II died at the start of the Second Egyptian–Ottoman War, the news reached Istanbul that the empire's army had just been defeated at Nizip by the army of the rebel Egyptian viceroy, Muhammad Ali. At the same time, the empire's fleet was on its way to Alexandria, where it was handed over to Muhammad Ali by its commander Ahmed Fevzi Pasha on the pretext that the young sultan's advisers had sided with Russia. However, through the intervention of the European powers during the Oriental Crisis of 1840, Muhammad Ali was obliged to come to terms, and the Ottoman Empire was saved from further attacks while its territories in Syria, Lebanon and Palestine were restored. The terms were finalised at the Convention of London (1840) which saved the empire from greater embarrassment.

Like his father, Abdülmecid was an advocate of reforms and was lucky enough to have the support of progressive viziers such as Mustafa Reşit Pasha, Mehmet Emin Âli Pasha and Fuad Pasha. Abdülmecid was also the first sultan to listen directly to the public's complaints on special reception days, which were usually held every Friday. Abdülmecid toured the empire's territories to see in person how the Tanzimat reforms were being applied. He travelled to İzmit, Mudanya, Bursa, Gallipoli, Çanakkale, Lemnos, Lesbos and Chios in 1844 and toured the Balkan provinces in 1846. In compliance with his father's express instructions, Abdülmecid immediately carried out the reforms to which Mahmud II had devoted himself. On 3 November 1839, the Edict of Gülhane, also known as Tanzimat Fermanı, was proclaimed, consolidating and enforcing these reforms.

By these enactments it was provided that the sultan's subjects of all classes should have their lives and property protected; that taxes should be fairly imposed and justice impartially administered; and that all should have full religious liberty and equal civil rights. The scheme met with strong opposition from the Muslim governing classes and the ulema, or religious authorities, and was only partially implemented, especially in the more remote parts of the empire. More than one conspiracy was formed against the sultan's life on account of it.