Sheikh Hamad's title changed to king when Bahrain switched from being an emirate to a kingdom in February 2002.
He had been crown prince since 1964, when, on the death of his father Sheikh Isa in March 1999, he became emir.
Born in 1950, he was educated at a public school in Cambridge, England, and went on to study at Mons Officer Cadet School in Aldershot, England, and at the US Army Command and Staff College, Fort Leavenworth, Kansas.
In 1968, he founded and became commander-in-chief of the Bahrain Defence Force (BDF). He served as minister of defence from 1971 to 1988.
The government has over the years faced protests from the Shia majority, with demonstrators saying the ruling Sunni minority shuts them out of housing, healthcare and government jobs.
Bahrain saw anti-government unrest in 2011 - inspired by uprisings in Tunisia and Egypt. The government used violence to try end the protests, in which some several people were killed. It also called in Saudi Arabian troops. However, protests and clashes continued into 2012.
"Bahrain Leaders Stats", NationMaster. Retrieved from http://www.nationmaster.com/country-info/profiles/Bahrain/Government/Leaders
"Bahrain Leaders Stats, NationMaster." 2013. <http://www.nationmaster.com/country-info/profiles/Bahrain/Government/Leaders>.
'Bahrain Leaders Stats, NationMaster', <http://www.nationmaster.com/country-info/profiles/Bahrain/Government/Leaders> [assessed 2013]
"Bahrain Leaders Stats", NationMaster [Internet]. 2013. Avaliable from: <http://www.nationmaster.com/country-info/profiles/Bahrain/Government/Leaders>.
"Bahrain Leaders Stats", NationMaster. Avaliable at: nationmaster.com. Assessed 2013.
"Bahrain Leaders Stats, NationMaster," http://www.nationmaster.com/country-info/profiles/Bahrain/Government/Leaders (assessed 2013)
"Bahrain Leaders Stats", NationMaster, http://www.nationmaster.com/country-info/profiles/Bahrain/Government/Leaders (last visited 2013)
"Bahrain Leaders Stats", NationMaster, http://www.nationmaster.com/country-info/profiles/Bahrain/Government/Leaders (as of 2013)