What you need to know:
- Angolan leader Jose Eduardo dos Santos stepped down in September 2017 after 38 years in charge. Never democratically elected, the former Marxist rebel died in July 2022 aged 79.
Cameroon President Paul Biya, who on Sunday marks 40 years in power, is Africa's second longest-serving leader after Equatorial Guinea's Teodoro Obiang Nguema Mbasogo.
But they are far from alone among leaders on the continent who have clocked up decades in office.
Here's a snapshot of Africa's ageing rulers:
Biya: Four decades
Cameroon has lived through 40 years of largely unchallenged and hardline rule under Biya.
The 89-year-old runs the country through a very small circle of aides, whom he appoints and banishes as he sees fit.
Openly talking about succession is taboo even for his closest supporters, and Biya has overseen a ruthless crackdown on dissent since his highly contested re-election in 2018.
- Obiang: Longest-serving -
Obiang, who came to power in an August 3, 1979 coup, is Africa's longest-serving leader, with 43 years at the helm. Next month, at the age of 80, he will run for a sixth term lasting seven years.
Nguesso: 38 years
In Congo-Brazzaville, Denis Sassou Nguesso, 78, has been in power for 38 years, albeit not uninterruptedly.
He was president from 1979 to 1992, then returned to office in 1997 after a civil war. He was re-elected in 2016 after the passing of a new constitution, then won a fourth mandate on March 21 this year.
Museveni: A sixth term
In Uganda, Yoweri Museveni, 78, has led his country for 36 years, since January 1986. He was re-elected in January 2021 for a sixth term after a contested campaign.
A Supreme Court ruling to abolish an age ceiling of 75 allowed him to stand once again and continue serving.
King Mswati III: In power at 18
Eswatini (formerly Swaziland), Africa's last remaining absolute monarchy, has been ruled by King Mswati III for 36 years.
He ascended to the throne in April 1986 aged just 18.
- Eritrea: 30th anniversary looms -
Isaias Afwerki, 76, has ruled the Horn of Africa nation with an iron fist since independence in May 1993.
Other African leaders in recent history also notched up huge spells in office.
The record-breaker is Emperor Haile Selassie of Ethiopia, who ruled for 44 years before being overthrown in 1974.
Libyan strongman Moamer Kadhafi held sway for almost 42 years. He was killed in 2011 as protests against his rule mushroomed into armed conflict.
Gabon's Omar Bongo Ondimba had been at the helm for 41 years when he died in June 2009.
Angolan leader Jose Eduardo dos Santos stepped down in September 2017 after 38 years in charge. Never democratically elected, the former Marxist rebel died in July 2022 aged 79.
Former Zimbabwean president Robert Mugabe, who died in September 2019 almost two years after being forced to step down, held office for more than 37 years.
In Sudan, Omar al-Bashir, who came to power in a coup in June 1989, remained in charge for 30 years until the military overthrew him in 2019.
In Chad, Idriss Deby Itno ruled for 30 years from December 1990 until his death in April 2021. He was succeeded by his son, General Mahamat Idriss Deby Itno.