Ossébi was born in Gamboma, located in Plateaux Region. At the Marien Ngouabi University in Brazzaville, he was a professor of sociology from 1982 to 1997. After Denis Sassou Nguesso returned to power in 1997, Ossébi headed the Presidency's Department of National Education, Human Resources, and Scientific Research from 1997 to 2002. He helped establish Acting Together for Congo, a political association supportive of President Sassou Nguesso that was launched on 9 February 2002, with Ossébi as its General Coordinator. On 18 August 2002, he was appointed to the government as Minister of Higher Education and Scientific Research, and he succeeded Pierre Nzila in that post on 21 August. His portfolio was reduced in scope on 3 March 2007, when he was appointed as Minister of Higher Education. In the June-August 2007 parliamentary election, Ossébi was Take Action for Congo's candidate in Abala constituency, located in Plateaux Region; he faced the candidate of the Congolese Labour Party, Gabriel Oba-Apounou, as well as an independent candidate, Joseph Mbossa. In the first round, Ossébi placed second behind Oba-Apounou, receiving 32.55% of the vote against 40.21% for Opa-Apounou. However, Ossébi prevailed in the second round, receiving 58.26% of the vote. During the campaign for the July 2009 presidential election, Ossébi worked on President Sassou Nguesso's re-election campaign as Spokesman for Political Affairs, a post he shared with François Ibovi. After winning re-election, Sassou Nguesso moved Ossébi to the post of Minister of Scientific Research on 15 September 2009. At the PCT's Sixth Extraordinary Congress, held in July 2011, Ossébi was elected to the PCT's 51-member Political Bureau. In a minor government reshuffle on 12 December 2011, he switched ministries with Bruno Itoua, becoming Minister of Energy and Hydraulics. For Ossébi, the move was viewed as a promotion to a more important ministry. In the July-August 2012 parliamentary election, Ossébi, this time standing as the PCT's candidate, was again elected to the National Assembly from Abala constituency; he won the seat in the first round with 79.95% of the vote. After Sassou Nguesso's victory in the March 2016 presidential election, he appointed Serge Blaise Zoniaba to replace Ossébi as Minister of Energy on 30 April 2016. Sassou Nguesso instead appointed Ossébi as Ambassador to UNESCO in 2017.
