President Muhammadu Buhari has renamed the national stadium in Abuja after the winner of the 1993 presidential election, Moshood Abiola.
Mr Abiola won that year's poll based on available results, but the election was cancelled by the military government of Ibrahim Babangida.
Mr Abiola later died in prison, months after he declared himself president.
President Buhari in 2018 recognised Mr Abiola's mandate by conferring on him the country's highest national honour of the Grand Commander of the Federal Republic, reserved only for presidents.
He also declared June 12, the day the election held, as Nigeria's democracy day. Since 1999, democracy day was celebrated on May 29. Wednesday was the first time the celebration happened on June 12.
In his speech at the event, which also marks Nigeria's 20th year of uninterrupted democracy, Mr Buhari said the national stadium will henceforth be known as Moshoo Abiola Stadium.
"I declared June 12 in memory of late Abiola and gave honour to him ... and I have also named the Abuja Stadium after Late Moshood Abiola," the president announced.
The event at the Eagles Square was attended by other foreign leaders, including the president of Rwanda, Paul Kagame.