He said only a great president, such as himself, could make Nigeria work for everyone.
The former governor made the announcement at the national headquarters of the Abdulkadir Abdulsalam-led faction of the Labour Party (LP), in Abuja, on Thursday, September 13, 2018.
Mimiko highlighted the "demonstrable track record" of his eight years as Ondo governor and touted himself to possess the ability to envision great ideas for the country.
He said Nigerians are capable of doing great things and only need the best hands to lead the country for it to achieve its potentials. He said only a great president, such as himself, could make Nigeria work for everyone.
He said, "I'm running because I know we can do better and we will do better. I know this because anywhere Nigerians find themselves, no matter the situation, we always rise above adversity.
"We don't just survive, we thrive. It is high time we replicated over this country that indomitable spirit of Nigerians. That spirit of accomplishment which has made stars of individual Nigerians all over the world.
"The only way to do this is by electing capable hands. It is by electing a great president that can drive this national vehicle to greatness. Without humility, I say to you, I'll make a great president for Nigeria."
The former governor also promised to challenge poverty, insecurity, discrimination against women, youth exclusion and despondency if elected president.
Shortly before Mimiko's declaration on Thursday, the party's National Publicity Secretary, Ebere Ifendu, cautioned Nigerians to disregard his declaration and the purported party convention slated for September 13.
She described Mimiko's declaration as an illegal event since Abdulsalam that sold him the expression of interest and nomination forms was removed as party chairman in 2017.
The statement read, "It has become necessary for the leadership of the Labour Party to draw the attention of the general public to the fraudulent collection of Expression of Interest and Nomination Form fees from innocent and unsuspecting political aspirants.
"That is for those who desire to contest various elective positions under the Labour Party through Alhaji A. A. Salam, the former national chairman of the party.
"It would be recalled that A. A. Salam was removed at the special national convention of the party held on 3rd October, 2017.
"This illegality was also confirmed by the Independent National Electoral Commission (INEC) report, presented by the three INEC officials that were detailed to supervise its conduct.
"Credible information reaching us revealed that A. A. Salam has concluded arrangements to pull a rented crowd to declare Olusegun Mimiko as the Labour Party's Presidential Candidate.
"This illegal event is schedule to hold in Abuja on Thursday, 13th September. This is a total violation of Article 27, section 1, subsection i and ii of the Labour Party’s constitution.
"Consequently, the party hereby disowns and rejects Olusegun Mimiko as its presidential candidate, since neither the national executive council nor the national convention has been notified, as provided in the party’s constitution referred to above."
Mimiko rejoined the Labour Party in June 2018 after initially dumping the party for the People's Democratic Party (PDP) in 2014.
He was elected Ondo governor in 2009 and re-elected in 2013 on the platform of the Labour Party after joining the party in 2006.