The Sepahsālār Mosque (Persian: مسجد سپهسالار – Masjed-e Sepahsālār) is a famous historic mosque in Tehran, Iran. The construction project of the mosque was started in 1879 upon the order of Mirza Hosein Sepahsalar, the Grand Vizir of Iran during Naser al-Din Shah Qajar, and the first phase of construction was finished after five years since it was started. The mosque was renamed the Shahid Motahhari, after the 1979 Iranian Revolution, but it is commonly known by its initial name of Sepahsalar Mosque.

The Sepahsalar Mosque is one of the largest mosques in Tehran. During the late Qajar as well as the Pahlavi era, the Sepahsalar mosque was a distinctive landmark of Tehran with its eight minarets which was unique in the Persian design of mosques.

The mosque is located southeast of Baharestan square, next to the former National Consultative Majlis of Iran. The Sepahsalar Mosque is the first mosque in Tehran whose design is a mix of Persian architecture and the architecture of mosques in Istanbul. The building is inspired by the Jameh Mosque of Isfahan, Chaharbagh School, and Sultan Ahmed Mosque. The mosque has a special dome and eight minarets.

The main entrance portal and the facade are of a quite distinctive Qajar style. Two massive minarets flank the recessed entrance, which leads into a courtyard surrounded by twin-storeyed arcades of college rooms; in all, there are some 60 chambers.

Tiles with full-blown floral motifs in typically flamboyant Qajar style decorate the courtyard, while a tile inscription band gives details of the original endowment. The prayer hall dome, 37m in height, is supported by 44 columns.