Many organizations, parties and guerrilla groups were involved in the Iranian Revolution. Some were part of Ayatollah Khomeini's network and supported the theocratic Islamic Republic movement, while others did not and were suppressed. Some groups were created after the fall of the Pahlavi Dynasty and still survive; others helped overthrow the Shah but no longer exist.
Before the Iranian Revolution, opposition groups tended to fall into three major categories: constitutionalist, Marxist, and Islamist.
Constitutionalists, including National Front (Iran), wanted to revive constitutional monarchy including free elections. Without elections or outlets for peaceful political activity though, they had lost their relevance and had little following.
Marxists groups were primarily guerrilla groups working to defeat the Pahlavi regime by assassination and armed struggle. They were illegal and heavily suppressed by the SAVAK internal security apparatus. They included the Tudeh Party of Iran; the Organization of Iranian People's Fedai Guerrillas (OIPFG) and the breakaway Iranian People's Fedai Guerrillas (IPFG), two armed organizations; and some minor groups. Although they played an important part in the revolution, they never developed a large base of support.
Islamists were divided into several groups. The Freedom Movement of Iran was formed by religious members of the National Front of Iran. It also was a constitutional group and wanted to use lawful political methods against the Shah. This movement comprised Bazargan and Taleqani. The People's Mujahedin of Iran was a quasi-Marxist armed organization that opposed the influence of the clergy and later fought the Islamic government. Individual writers and speakers like Ali Shariati and Morteza Morahhari did important work outside of these parties and groups.