Otto (Greek: Όθων, romanized: Óthon, German: Otto Friedrich Ludwig von Bayern; 1 June 1815 – 26 July 1867) was a Bavarian prince who ruled as King of Greece from the establishment of the monarchy on 27 May 1832, under the Convention of London, until he was deposed on 23 October 1862.

The second son of King Ludwig I of Bavaria, Otto ascended the newly created throne of Greece at age 17. His government was initially run by a three-man regency council made up of Bavarian court officials. Upon reaching his majority, Otto removed the regents when they proved unpopular with the people, and he ruled as an absolute monarch. Eventually his subjects' demands for a constitution proved overwhelming, and in the face of an armed (but bloodless) insurrection, Otto granted a constitution in 1843.

Throughout his reign Otto was unable to resolve Greece's poverty and prevent economic meddling from outside. Greek politics in this era were based on affiliations with the three Great Powers that had guaranteed Greece's independence, Britain, France and Russia, and Otto's ability to maintain the support of the powers was key to his remaining in power. To remain strong, Otto had to play the interests of each of the Great Powers' Greek adherents against the others, while not irritating the Great Powers. When Greece was blockaded by the British Royal Navy in 1850 and again in 1854, to stop Greece from attacking the Ottoman Empire during the Crimean War, Otto's standing amongst Greeks suffered. As a result, there was an assassination attempt on Queen Amalia, and finally in 1862 Otto was deposed while in the countryside. He died in exile in Bavaria in 1867.