He has ruled with an iron fist, repressing all political and armed opposition, and holding on to power in the face of social upheaval, economic inequality and separatist violence.
Biya’s advanced years and his long absences from the public eye when he visits Swiss hotels have for years prompted speculation about his health and even rumours that he has died.
Yet the glaring difference in age between the President and an increasingly frustrated youthful population is not confined to Cameroon.
The spectacle of decrepit autocrats ruling over youthful populations and grimly hanging on to power for decade after decade is so common in Africa it has become a cliche.
In 1986, when Yoweri Museveni took power in Uganda by ousting the military regime of General Tito Okello, he singled out the issue as a cause of the continent’s ills.
He said: “The problem of Africa in general and Uganda in particular is not the people but leaders who want to overstay in power”.
As if to prove his point, 39 years later Museveni is still in power after removing term limits and is now 81 in a country where the median age is just 17.
Africa currently accounts for seven of the world’s 10 longest serving leaders, excluding monarchs.
Some countries with long-serving leaders have seen strong economic growth and periods of stability, for example in Ivory Coast and Rwanda.
Yet ageing autocrats often come with a cost of repression, corruption, and the destruction of political opposition.
Recent research has also suggested there are diminishing returns as African leaders cling to power, as the methods they use to hang on feed corruption, repression, and damage overall governance, holding their countries back.
A study by Nic Cheeseman, of the University of Birmingham, and Marie-Eve Desrosiers, of the University of Ottawa, found that once leaders start to scrap term limits and settle in for long stints, there is a corrosive effect on the rule of law and leaders have fewer incentives to do a good job.
Corruption grows and leaders’ patronage often starts to focus on narrow inner circles and family groups.
The continent’s elderly leaders may also find themselves on a collision course with Africa’s demographic forces.
The median age of sub-Saharan Africa is only around 20 and some 70% of the population is aged under 30.
Recent so-called ‘Gen Z’ social media-organised protests by crowds in their teens and 20s against the status quo have erupted in African countries including Kenya, Togo, Madagascar, and Morocco.
While the protests in each country have had different triggers, they have often had a broad desire to remove entrenched, corrupt regimes which are failing to govern.
Faced with these “dinosaurs”, some young African leaders make a virtue of their youthful vigour.
Ibrahim Traore became the youngest leader on the continent after a 2022 coup brought him to power in Burkina Faso at the age of 34.
A skilful Kremlin-backed propaganda campaign promotes him as a youthful pan-African role model in contrast to Western-backed old-timers.
In Uganda’s elections next year, Museveni will take on pop star-turned-politician Bobi Wine who at 43 is 38 years his junior.
Yet elsewhere, leaders continue to try to extend their stay in the presidential palace.
The day before Biya celebrated his latest seven-year term, Djibouti’s parliament opened the way for its own President, Ismail Omar Guelleh, to run for a sixth term after removing age limits.
Guelleh, 77, has held power since 1999 in the tiny Horn of Africa nation, but had been due to be blocked from running again by a constitutional rule decreeing that the head of state cannot run for office after 75.
In Equatorial Guinea, Teodoro Obiang Nguema Mbasogo, 83, has ruled since 1979, making him the world’s longest-serving president.
He has presided over an oil boom, which has now peaked, and has been accused of corruption and rights abuses, which he denies.
And in Togo, Jean-Lucien Savi de Tove, 86, assumed office last May under a constitutional shift to a parliamentary system, becoming Togo’s oldest president.
The shift allowed Faure Gnassingbe, the former president, to continue to lead the government, extending an unbroken dynastic tenure that began when Gnassingbe Eyadema, his late father, came to power in 1967 after a coup.
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