Speculation has Bernie Sanders may run for US President in 2020, when he will be 79. Mahathir Mohamad is aiming to become Malaysias PM (again) at the age of 92.
Wikipedia has a list of state leaders by age. Many of the oldest state leaders are constitutional or absolute monarchs or presidents who have been in power for a long time. But who is the oldest head of state / government at the time of being elected to the office?
For the purpose of this question, I consider any election where the person did not hold office before, but did hold office after the election. I include cases of de facto elections, such as the leader of the largest party becoming prime minister after elections, as widely expected but not required in parliamentary systems.