Sri Sultan Hamengkubuwono X (Javanese: ꦯꦿꦶꦯꦸꦭ꧀ꦡꦟ꧀ꦲꦩꦼꦁꦑꦸꦨꦮꦟ꧇꧑꧐꧇, also spelled as Hamengkubuwana X, often abbreviated as HB X; born Bendara Raden Mas Herjuno Darpito, 2 April 1946) is the Sultan of the historic Yogyakarta Sultanate in Indonesia. Since 1998, he has also served as Governor of the Special Region of Yogyakarta (Daerah Istimewa Yogyakarta).
Hamengkubuwono X succeeded his father, Hamengkubuwono IX, as the Sultan of Yogyakarta when Hamengkubuwono IX died on 3 October 1988. Hamengkubuwono X was formally installed as Sultan on 7 March 1989. However, the position of the Governor of the Yogyakarta Special Region did not go to Hamengkubuwono X. Vice Governor Sri Paku Alam VIII, prince of the subordinate enclave of Paku Alaman within Yogyakarta, was instead controversially elevated to the position of governor. This was contrary to the agreement made at the time of Indonesia's independence in recognition of Hamengkubuwono IX's support and role in the Indonesian War of Independence. Under the agreement, the Sultan holds the position of governor in the Yogyakarta Special Region, and the Paku Alam holds the position of vice governor.