Ahmadinejad, the son of a blacksmith, grew up in Tehrān, where in 1976 he entered the Iran University of Science and Technology (IUST) to study civil engineering. During the Iranian Revolution (1978–79), he was one of the student leaders who organized demonstrations. After the revolution, like many of his peers, he joined the Revolutionary Guards, a religious militia group formed by Ayatollah Ruhollah Khomeini (Khomeini, Ruhollah). Parallel to his service with the Revolutionary Guards in the Iran-Iraq War (1980–88), he continued his studies at IUST, eventually earning a doctorate in transportation engineering and planning. Following the war he served in various positions until 1993, when he was appointed governor of the newly established Ardabīl province. After his term as governor ended in 1997, he returned to IUST as a lecturer.

Ahmadinejad helped establish Abadgaran-e Iran-e Islami (Developers of an Islamic Iran), which promoted a populist agenda and sought to unite the country's conservative factions. The party won the city council elections in Tehrān in February 2003, and in May the council chose Ahmadinejad to serve as mayor. As mayor of Tehrān, Ahmadinejad was credited with solving traffic problems and keeping prices down.

In 2005 Ahmadinejad announced his candidacy for the presidency of Iran. Despite his service as mayor of the capital city, he was largely considered a political outsider, and opinion polls showed little support for him prior to the first round of elections. Through a massive nationwide mobilization of supporters and with the support of hard-line conservatives, however, Ahmadinejad managed to secure one-fifth of the vote, which propelled him into the second round of balloting, in which he easily defeated his more moderate rival, former president Hashemi Rafsanjani (Rafsanjani, Hashemi). He was confirmed president on August 3 by Ayatollah Ali Khamenei (Khamenei, Ali).

As president, Ahmadinejad presented himself as a populist, initially focusing on issues such as poverty and social justice. His first months in office were characterized by internal challenges brought about by a sweeping changing of the guard in all key positions. In contrast to his reform-oriented predecessor, Mohammad Khatami (Khatami, Mohammad), Ahmadinejad generally took a more conservative approach domestically, in 2005 prohibiting state television and radio stations from broadcasting music considered “indecent,” though under his leadership women symbolically were allowed for the first time since the revolution into major sporting events. Ahmadinejad was very active in foreign affairs, vigorously defending Iran's nuclear program against international criticism, particularly from the United States and the European Union. He also prompted international condemnation with comments calling for Israel to be “eliminated from the pages of history” (sometimes translated as calling for Israel to be “wiped off the map”) and for labeling the Holocaust a myth. His confrontational style was sometimes subject to criticism internally as well, and in December 2006 local elections, his allies lost ground to moderates.