Benin: Patrice Talon was sworn in as Benin's president
Benin's leader can serve two terms but Talon has said he will step down after five years to avoid "complacency" and seek to limit future presidents to a single term.
The West African country is seen as a bastion of democracy and stability in a troubled region where military coups are a regular occurrence and polls are often marred by violence.
"My mandate will be a mandate of rupture, transition and reforms," said Talon, adding that he would strive to combat corruption, improve the economy and fight terrorism.
"I will make diplomacy an instrument of cooperation for development," he told a crowd estimated by organizers at 20,000 at the ceremony in the capital Porto-Novo.
Benin already contributes to a multinational task force fighting Boko Haram, a militant group that is based in the northeast of the country's giant neighbour Nigeria.
Talon is a cotton magnate who handily beat former prime minister Lionel Zinsou in a run-off election last month. Zinsou was the preferred choice of former president Thomas Boni Yayi, who stepped down after 10 years in power.
Benin's minister for energy and water resigned in May amid a corruption scandal that caused the Netherlands to suspend aid after $4 million went missing in 2014 from a project to improve the nation's water supplies.
Talon, who was educated in Senegal and France, once supported Boni Yayi but the two fell out and the then president accused him of being involved with a plot to poison him.
Talon sought exile in France but was later pardoned, returning to Benin in October.