Benin's ruling party candidate, Prime Minister Lionel Zinsou, has failed to secure more than 50% in Sunday's presidential elections, taking the contest into a second round.
Preliminary results show he took 28% of the vote and will face businessman Patrice Talon, who won 25%.
Thirty three candidates contested to replace President Thomas Boni Yayi, who is stepping down after two terms.
The date for the run-off vote is yet to be announced.
The provisional results must be confirmed by the constitutional court.
Correspondents say a challenge appears possible, particularly as another businessman, Sebastien Ajavon, finished less than 2% behind Mr Talon.
Mr Zinsou, who is Franco-Beninese, used to head France's largest investment bank and is considered as "France's candidate" by his detractors.
Benin gained independence from France in 1960.
Top five candidates:
- Lionel Zinsou - 28.4%
- Patrice Talon - 24.8%
- Sebastien Ajavon - 23.03%
- Abdoulaye Bio Tchane - 8.79%
- Pascal Jean Irenne - 5.85%
Source: Benin's electoral commission
The West African nation introduced multi-party democracy in 1990 after nearly two decades of military rule - the first to do so in sub-Saharan Africa.
Sunday's election was delayed after problems with the distribution of polling cards to the 4.7 million registered to vote, an issue that continued until the day before the poll.
Benin's constitution barred Mr Boni Yayi from seeking a third term, although he had tentatively sought changes to the text allowing him to do so.
The rulers of other African countries such as Burundi, Rwanda and Congo-Brazzaville have recently changed their constitutions to allow third terms.