President: Denis Sassou Nguesso
Denis Sassou Nguesso is one of Africa's longest-serving leaders, having first come to power three decades ago.
He gained his latest seven-year term after elections in July 2009 which were boycotted by the opposition, and from which the main opposition candidate was excluded.
He was installed as president by the military in 1979 and lost his position in the country's first multi-party elections in 1992.
He returned to power in 1997 after a brief but bloody civil war in which he was backed by Angolan troops.
A French-trained paratrooper colonel, Mr Sassou Nguesso is seen as a pragmatist. During his first presidency in 1979-92 he loosened the country's links with the Soviet bloc and gave French, US and other Western oil companies roles in oil exploration and production.
He abandoned the one-party system in 1992, opening the ruling Congolese Workers Party (PCT) to competition after more than 20 years as the sole party.
But he has also been dogged by corruption allegations. In May 2009, a French judge announced an investigation into whether Mr Sassou Nguesso and two other African leaders - all of whom deny wrongdoing - had plundered state coffers to buy luxury homes and cars in France.
In 2015, a national dialogue organised by Mr Sassou Nguesso recommended that the constitution be changed to allow the president to stand for what be his third term since returning to power in 1997.
The opposition, which boycotted the process, condemned the move as a constitutional coup.
Denis Sassou Nguesso was born in a village in northern Congo in 1943. In 2006 he became chairman of the 53-nation African Union.