LIBREVILLE, Gabon — Behind the tall white walls of a grandiose home belonging to the world’s longest-ruling president, ostriches, buffalo, and camels roam neatly landscaped lawns — part of a vast private complex said to include a crocodile wetland and lake topped with lotus flowers.

In the poverty-stricken shell of a city outside, where the poorest pick through garbage for scraps to eat, Omar Bongo’s mustachioed face is omnipresent: gazing solemnly from glass building façades, beaming proudly from ubiquitous billboards, woven into the fabric of countless shirts worn from the coast to the farthest reaches of the forested interior.

He may be short in stature, but he is larger than life in the oil-rich Central African nation he has ruled for 40 years — so long that he’s the only president most of his subdued 1.5 million people (life expectancy, 53) have ever known.

Mr. Bongo became the longest-ruling head of state, not counting the monarchs of Britain and Thailand, after Fidel Castro resigned last month, ending 49 years in power.

While most Gabonese genuinely fear the 72-year-old autocrat and there is little opposition, many accept his rule because he has kept his country remarkably peaceful and governed without the sustained brutality characteristic of many dictators.

“God brought him to us and only God can call him away,” said a forestry worker, Ignasse Minaga, who was born the same year Mr. Bongo became president, in 1967. “For us there is only Bongo. He is irreplaceable.”