Emir: Sheikh Tamim bin Hamad al-Thani
Sheikh Tamim bin Hamad al-Thani assumed the role of emir when his father abdicated in June 2013.
The voluntary hand-over by Sheikh Hamad bin Khalifa al-Thani was a rare step for a ruler in a region where leaders normally die in office.
Diplomats have said the outgoing emir, who overthrew his father in a bloodless coup in 1995, had long planned to abdicate in favour of his son. In his abdication speech he said it was time for a new generation to take over.
Sheikh Tamim, aged 33 at the time he took power, is the second son of the emir and his second wife Sheikha Mozah.
He is deputy commander of the armed forces and head of the National Olympic Committee, and in recent years had taken on increasing military and security responsibilities.
Like his father he went to the British military academy Sandhurst.
He also went to Sherborne school in Dorset, United Kingdom.
Analysts did not expect major changes to foreign policy or domestic plans after the handover to Sheikh Tamim, who had been involved in running the country under his father's direction.