The former president's decision to run has him at odds with Iran's supreme leader Ayatollah Ali Khamenei who has ordered Ahmadinejad to stay out of the race.
Iran's former president Mahmoud Ahmadinejad said he will run for office in the presidential elections in May.
Speaking at a press conference in Tehran, Ahmadinejad said he was signing up as a candidate to support his former vice president, Hamid Baghaei, another presidential hopeful.
"There is extensive pressure on me from dear people of different walks of life as their small servant to come to the election scene," he said.
Iran's supreme leader, Ayatollah Ali Khamanei, had previously ordered him not to run. The Ayatollah is the head of state and highest ranking political and religious authority in the country and appoints the heads of many powerful posts in the military, the civil government, and the judiciary.
"Khamenei advised me against participating in this election as a candidate. I accepted that. However, his advice did not mean I am barred from running," Ahmadinejad said.
"He said he was not telling me either to come or not to come. It was just advice and his advice does not prevent me from running," he added.
TRT World spoke to Amin Darban, who has more on this story from Iran's capital Tehran.