Moncef Marzouki and Beji Caid Essebsi will face off on December 21 in Tunisia's second round of presidential voting to decide who leads the nation that sparked the Arab Spring.
"Voting will take place on December 21," the head of the ISIE electoral organising body, Chafik Sarsar, told a news conference on Monday.
The secularist leader Essebsi has beaten the incumbent Marzouki in the first round of the country's landmark presidential election, but the two men did not gain enough votes to prevent a runoff.
More than three years since longtime ruler Zine el-Abedine Ben Ali was ousted by a popular uprising, Tunisia has been able to adopt a new constitution, and rival secularists and Islamist parties have largely avoided the turmoil that has plagued other Arab states swept by popular revolts.
The Islamist Ennahda Party did not field or endorse a candidate in the presidential elections, but its supporters are believed to be backing Marzouki.