The Imamzadeh Seyed Morteza (; ), or simply Imamzadeh Morteza, is a Shi'ite imamzadeh located in Kashmar, in the province of Razavi Khorasan, Iran. It was completed in 1857 CE, during the Qajar era.
The complex was added to the Iran National Heritage List on 24 October 1977, administered by the Cultural Heritage, Handicrafts and Tourism Organization of Iran. The complex is one of the holiest sites in Twelver Shia Islam.