Mohammad Hosseini Beheshti (Persian: محمد حسینی بهشتی; 24 October 1928 – 28 June 1981) was an Iranian jurist, poetic philosopher, cleric and politician who was known as the second person in the political hierarchy of Iran after the Revolution. Beheshti is considered to have been the primary architect of Iran's post-revolution constitution, as well as the administrative structure of the Islamic republic. Beheshti is also known to have selected and trained several prominent politicians in the Islamic Republic, such as former presidents Hassan Rouhani and Mohammad Khatami, Ali Akbar Velayati, Mohammad Javad Larijani, Ali Fallahian, and Mostafa Pourmohammadi. Beheshti also served as the Secretary General of the Islamic Republic Party, and was the head of the Iranian judicial system. He further served as Chairman of the Council of Islamic Revolution, and the Assembly of Experts. Beheshti earned a PhD in philosophy, and was fluent in English, German and Arabic.

On 28 June 1981, Beheshti was assassinated in the Hafte tir bombing by the People's Mujahedin of Iran (MEK), along with more than 70 members of the Islamic Republic Party, including four cabinet ministers and 23 members of parliament. The Iranian government blamed Mohammad Reza Kolahi as the MEK operative involved in the incident. Following his death, Ayatollah Khomeini referred to Beheshti as a person who was "as a nation for us."

Beheshti was born in Isfahan in 1928. He studied both at the University of Tehran and under Muhammad Husayn Tabatabaei in Qom. Between 1965 and 1970, he led the Islamic Center in Hamburg where he was responsible for the spiritual leadership of religious Iranian students in Germany and western Europe. In Hamburg, he also worked with Mohammad Khatami and was among his influences. From the early 1960s he was involved in activities against the monarchy and was arrested several times by the Shah's secret police, the SAVAK.

Beheshti joined Ayatollah Khomeini in Najaf, Iraq, where the latter was in exile. There he became part of Khomeini's underground movement.

Following the Islamic revolution, Beheshti became one of the original members of the Council of Revolution of Iran and soon its chairman. As vice-president, he played a particularly important role in promoting the principle of velayat-e faqih as the basis for the new constitution. In the first post-revolutionary Iranian parliament, he led the Islamic Republic party together with Ali Akbar Hashemi Rafsanjani. (However, he never campaigned for the parliament, for he was already the head of Iran's Supreme Judicial System). Behesti was the founding member, first general secretary and a central committee member of the party. He was also planning to run for the presidency in the first presidential elections, but withdrew after Ayatollah Khomeini told a delegation of Rafsanjani and Khamenei that he preferred non-clerics as presidents, which led to the Islamic Republic party's endorsement of (firstly) Jalaleddin Farsi and (subsequently) Hasan Habibi as candidate.

On 28 June 1981, Beheshti was killed in the Hafte tir bombing during a party conference. A spokesman for Iran's revolutionary guards said in an interview that a People's Mujahedin of Iran member, Mohammad Reza Kolahi, had been responsible.

According to James Buchan, the Islamic Republic of Iran first blamed the Tudeh Party, SAVAK, and the Iraqi regime. Two days later, Ruhollah Khomeini accused the MEK. A few years later, a Kermanshah tribunal executed four "Iraqi agents" for the incident. Another tribunal in Tehran executed Mehdi Tafari for the same incident. In 1985, the head of military intelligence informed the press that this had been the work of royalist army officers. Iran's security forces blamed the United States and "internal mercenaries".

Along with Beheshti, many clerics, ministers, and officials also died in the bombing. Supreme Leader Ayatollah Khomeini was reportedly very moved by Beheshti's death. A commemoration ceremony is organized each year on the day of Beheshti's assassination.