The straight-talking retired brigadier, who briefly led a junta in 1996, beat Samura Kamara to end a decade in power for the All Peoples’ Congress (APC) in last month’s run-off, according to official results.
A member of the Mende people who traditionally lend strong support to the opposition Sierra Leone People’s Party (SLPP), Bio was born on May 12, 1964, in the southern town of Tihun.
After school and military training, he was sent in 1990 to neighbouring Liberia, where war had just broken out, to serve in the Sierra Leone contingent of troops sent by the Economic Community of West African States (ECOWAS).
He was recalled to his own nation one year later when rebel forces there began to stir, with the rumblings of Sierra Leone’s own civil war on the horizon.
The former military man was one of a group of young soldiers behind a 1992 coup that would install their leader, Valentine Strasser, as the youngest head of state in the world, at age 25.
Bio ousted Strasser four years later and headed the government for three months to pave the way for democratic elections.
He agreed to step aside for the duly elected Ahmad Tejan Kabbah, allowing Sierra Leone to re-establish democracy.
He later apologised for the conduct of troops who executed more than 20 people after the 1992 coup, and is widely considered to have rehabilitated his image.
Bio, who spent time after leaving power studying in the United States, is not known to mince words.
During a February campaign debate he called Chinese infrastructure projects “a sham with no economic and development benefits to the people” of the poor west African country.
After gaining the presidential nomination for the SLPP in 2012, he lost the election to outgoing president Ernest Bai Koroma.
This time, he has promised to review mining concession agreements and to provide free universal education at the primary and secondary levels if elected.
After Bio hit out at corruption on the campaign trail, his opponent Kamara accused the SLPP candidate of stealing $18 million during his brief time at the helm, though his APC opponent faces corruption allegations of his own.
The SLPP has accused the APC of wanting to cling to power after a lawyer linked to the ruling party filed a complaint of electoral fraud which briefly delayed the vote.