Ouellet, a theologian of prestige, 68, provoked strong controversy in Quebec, the French-speaking province of Canada in 2000 by defending the Vatican's position against gay marriage and against abortion, including in cases of rape, and criticized the "decay" of a society in which two out of every three children are born out of wedlock.
The Canadian press dubbed him the "Iron Cardinal."
"He is the only cardinal who meets the Pope every week," said the retired Archbishop of Montreal Jean-Claude Turcotte, commenting on the trusting relationship between Ouellet and Benedict XVI, who officially abdicated the pontificate on Feb 13.
The polyglot Cardinal (who speaks French, English, Spanish, Portuguese, German and Italian), bronzed by the sun of Italy, is discrete and has no media profile. He has a reputation as a man of action, who does not hide his beliefs to the point of trying to convince those who do not share them.
Third in a family of eight children, Marc Ouellet was born in June 1944 in an area of northern Quebec which ar the time had only recently been inhabited. A region of lumberjacks and gold mines.
His father was a school principal. At 17, he read the "Introduction to the Devout Life" by St. Francis de Sales, and this young, strong and athletic, swimming and hockey fan, decided to become a priest.
Ouellet graduated in theology in Montreal at the time that Quebec society,guardian of French language and traditions after the British conquest in 1760, was beginning to turn their backs on the Catholic Church. In 1968 he was ordained priest.
Between the years 1970 and 1980, he spent long periods in Colombia, where he trained thousands of religious as dean and professor of seminaries in Manizales, Cali and Bogotá.
After his appointment as rector of the Grand Seminary of Montreal in 1990, his career made a dazzling ascent. In 2001 he was appointed bishop and archbishop a year later.
In 2003, John Paul II appointed him Cardinal and two years later when the Pope died, Ouellet first appears among the candidates with the potential of becoming Pope.
Benedict XVI appointed him in 2010 as Prefect of the Congregation for Bishops and President of the Pontifical Commission for Latin America, a body of the Roman Curia (the Vatican administration).
At the end of that year, his ability and temperament shone forth at the international congress "Ecclesia in America", the event which opened the Year of Faith decreed by Pope Benedict XVI.
In 2011, when a Quebec newspaper asked him about the chances of becoming pope, Ouellet said: "It would be a nightmare ... an overwhelming responsibility."
However, this week he admitted in an interview with Radio Canada, that it is a position he should "be prepared" for in any eventuality.
"Should I go to the conclave thinking, 'and if it happens ...', '... and if it happens'. I confess that it makes me think, pray, and also generates a bit of fear," he said, before noting that the future Pope should address, among other major issues, new media, given their great influence on young people.
But a major obstacle may arise in the path of Ouellet to the Throne of Peter. Victims of clergy sexual abuse this week published a list of 12 papabile who have allegedly covered up such crimes, in which the Canadian appears alongside cardinals of Argentina, Australia, United States, Ghana, Honduras, Italy, Mexico and the Czech Republic.
"We want to encourage Catholic prelates to stop pretending that the worst is over regarding the clergy sexual abuse and to stop hiding the crisis," said David Clohessy, director of Survivors Network of those Abused by Priests (SNAP), based in the USA.
"Tragically, the worst is almost certainly going to happen," he added.