Sheikh Tamim bin Hamad Al Thani became one of the youngest emirs in Qatar's history when he assumed power in June 2013 at the age of 33.
Sheikh Tamim took over from his father, Sheikh Hamad bin Khalifa Al Thani, who spent nearly two decades at the country's helm before stepping aside.
Sheikh Tamim attended Sherborne School, Harrow School and the Royal Military Academy Sandhurst in the UK, from which he graduated in 1998.
He has served in a number of diverse roles, including president of the Qatar National Olympic Committee, deputy commander-in-chief of the Qatar Armed Forces, chairman of the committee organising the 2022 FIFA World Cup, chairman of the Supreme Education Council and chairman of the Qatar Investment Authority, the country's sovereign wealth fund.
In announcing the handover of power to his son in 2013, Sheikh Hamad said: "I am fully certain that he is up to the responsibility, deserving the confidence, capable of shouldering the responsibility and fulfilling the mission."
Sheikh Tamim had been named heir apparent in 2003, when his elder brother stepped aside. Saudi Arabia's King Abdullah was quick to offer congratulations after the transfer of power in 2013.
"We are confident that you will continue the journey of your father ... and his efforts in serving the state of Qatar and its brotherly people as well as strengthening relations between the two nations," King Abdullah said.
The United Arab Emirates (UAE) also lauded the handover, affirming the "deepness of the brotherly relations" between the countries.
The emir's father, Sheikh Hamad, initially came to power in 1995, declaring himself ruler while his own father was on an overseas trip.
Qatar's economy has grown significantly in the intervening decades, thanks largely to production from its massive natural gas reserves. The economy grew from $8bn in 1995 to $174bn a decade and a half later.
During most of Sheikh Hamad's rule, Qatar adopted a pragmatic policy, cultivating relationships with countries and groups across the political spectrum and acting as a regional mediator on various issues, including internal Palestinian divisions. Qatar also emerged as a strong supporter of the Syrian opposition.
Sheikh Hamad maintained close ties with the United States, which for decades has flown warplanes from a major military base in Qatar. But he also built cordial ties with Iran, which most of Qatar's neighbours regard as a serious threat; the two countries share control of the world's largest natural gas field.
When he took the reins in 2013, Sheikh Tamim had already been deeply involved in Qatari decision-making for years.
A year later, in 2014, the Gulf Cooperation Council was gripped by a diplomatic spat as Saudi Arabia, the UAE and Bahrain criticised Qatar over its support for the Muslim Brotherhood, a group labelled as a "terrorist organisation" by Saudi Arabia and the UAE. The countries reconciled months later, and ambassadors who had been expelled were returned to Qatar.
A new rift emerged in 2017 after hackers targeted the Qatar News Agency and posted comments purportedly criticising US foreign policy, attributed to Sheikh Tamim.
In the days that followed, several Arab nations cut ties with Qatar, accusing it of "harbouring a multitude of terrorist and sectarian groups that aim to create instability in the region".
Qatar has rejected the allegations as having "no basis in fact".