Ali Abdullah Saleh, 64, became president of the then-North Yemen in 1978 and has been in power ever since.
His main achievement is the reunification of Yemen, of which he became president when north and south merged in May 1990.
Four years later, he preserved the unity of his Arabian peninsula republic by force, crushing a southern secession attempt with the help of some Arab countries, mainly Iraq.
In December 1997, parliament promoted him to the rank of field marshal "in recognition of his historic and national role in building the new Yemen."
Saleh, a pragmatist, has managed to survive several crises, including Saddam Hussein's invasion of Kuwait in 1990, when Saudi Arabia punished Yemen for siding with Iraq.
Riyadh expelled about 700,000 Yemeni expatriate workers, depriving their impoverished country of remittances that constituted one of its main revenues.
Saleh's rule relies on the army and Yemen's ruling party, the GPC, a hodgepodge of civil servants and representatives of urban and rural communities, but also on the crucial support of tribes, which form the backbone of Yemeni society.
His ability to juggle many different groups for so long in a country as complex as Yemen shows what a master tactician he is.
After Yemen's unification, Saleh launched a cautious reform process, introducing a multi-party system and giving the press a margin of freedom. He organised legislative elections in 1993 and 1997 and a presidential ballot in 1999.
His only rival in the 1999 election was Najib Qahtan al-Shaabi, an "independent" member of Saleh's party and son of the first president of former South Yemen. Shaabi won 3.7% of the vote.
Saleh, a stocky figure with piercing eyes and a thin moustache, had no trouble replacing his military uniform with elegant suits.
With only a limited education, he joined the army at an early age and took part in the 1962 coup that overthrew the Zaidi imamate and installed a republic.
His leadership skills were quickly noticed and enabled him to climb the ladder of power.
After the June 1978 assassination of president Ahmad al-Ghashmi, Saleh was elected president of North Yemen by a constituent assembly.
He surrounded himself with close aides, notably his brothers, whom he named to key military and security posts.
Saleh is a member of the Zaidi community, a sect that embraces an Arab version of Shia belief different from Iranian Shia beliefs seen in Iraq, Lebanon, Syria and Gulf countries. The Zaidi sect, known for its closeness to Sunni teachings, is dominant in northwest Yemen but forms a minority of around 30% in the mainly Sunni Muslim country.
The Yemeni leader hails from the Sanhan tribe, part of the powerful Hashed tribal confederation.
Saleh is known for his pan-Arab leanings. He entered a short-lived Arab union with Iraq, Jordan and Egypt in 1989. The union collapsed when Iraqi forces invaded Kuwait in 1990.
Saleh is married and has seven sons, including Ahmad, a 37-year-old lieutenant colonel in charge of the Republican Guard and special forces who is seen as a possible successor, though the subject is taboo in Yemen.