The Manne Siegbahn Laboratory (MSL) was a research facility, during its last years a part of Fysikum, the physics department of Stockholm University. MSL was situated in the Manne Siegbahn building, which is located just north of the underground station "Universitetet". The laboratory was performing research and development in accelerator physics. In the last period of its existence, the activities at the laboratory included the design and construction of the double electrostatic storage ring DESIREE, and participation in the FLAIR project and in the Stockholm-Uppsala Centre for Free Electron Laser Research. CRYRING was used for experiments in, mainly, atomic and molecular physics from 1992 to the end of 2009. It has now been moved to Darmstadt in Germany, where it will be used for deceleration of antiprotons and heavy ions at the FLAIR facility at FAIR. The laboratory was also building a small, double electrostatic storage ring DESIREE. Within the Stockholm-Uppsala Centre for Free Electron Laser Research MSL also participates in the development of the European XFEL at DESY in Hamburg, Germany. It has collaborated with the Karolinska Institute on development of equipment for cancer therapy. The laboratory was involved in several external activities, such as participation in the design study for EURISOL, the future European ISOL facility for radioactive beams; EBIS development together with JINR, Dubna; the REX-ISOLDE project where the laboratory has developed and built an EBIS ion source.