Cameroon President Paul Biya, 85, who is seeking a seventh consecutive term on Sunday, is the second longest-serving leader in Africa with nearly 36 years in office.
Only Teodoro Obiang Nguema of Equatorial Guinea is ahead, by three years.
Here is a rundown of the continent's leaders in longevity.
Mr Obiang, 76, has been the head of tiny, oil-rich Equatorial Guinea for 39 years. He came to power in a coup in August 1979 and was elected to a fifth seven-year term in 2016.
Cameroon's Biya became president in November 1982.
Congo-Brazzaville President Denis Sassou Nguesso has spent 34 years in office, but not in one go. He first served from 1979 to 1992 and returned in 1997 at the end of a civil war. Sassou Nguesso was re-elected in March 2016 and could run again when his current term expires.
In Uganda, Yoweri Museveni has been in power for 33 years. He took office in January 1986 after winning the war that ousted brutal dictator Idi Amin Dada. He was elected to a fifth term in February 2016.
In southern Africa's tiny eSwatini, the former Swaziland, King Mswati III is the continent's last absolute monarch. He took the throne in April 1986, more than 32 years ago.
In Sudan, Omar al-Bashir has ruled for 29 years after staging a coup in June 1989.
Chad's Idriss Deby took over the northern nation in 1990, giving him nearly 28 years in power. He won a disputed fifth term in April 2016.
The Eritrean leader Isaias Afwerki has been in charge since independence in April 1993, making 25 years.
Ethiopian emperor Haile Selassie holds the record for the longest time in power on the African continent. After reigning for 44 years, he was ousted in 1974.
Libya's Moamer Kadhafi, who ruled with an iron fist for nearly 42 years, was killed in 2011 after a protest movement turned into an armed conflict.
Gabon's Omar Bongo died in June 2009 after more than 41 years in power.
Angola's Jose Eduardo dos Santos stepped down in September 2017, having led his oil-rich country for 38 years.
Gnassingbe Eyadema also ruled the west African country of Togo for 38 years from 1967 to his death in 2005. He was succeeded by his son Faure Gnassingbe.
Zimbabwe's "father of independence" Robert Mugabe was forced out in November 2017 after 37 years at the helm.