A synchrotron is a particular type of cyclic particle accelerator originating from the cyclotron in which the guiding magnetic field (bending the particles into a closed path) is time-dependent, being synchronized to a particle beam of increasing kinetic energy. The synchrotron is one of the first accelerator concepts that enable the construction of large-scale facilities, since bending, beam focusing and acceleration can be separated into different components.

The first electron synchrotron was constructed by Edwin McMillan in 1945, although the principle had already been published (unknown to him) in a Russian journal by Vladimir Veksler. The first proton synchrotron was designed by Sir Marcus Oliphant and built in 1952.

A storage ring is a special type of synchrotron in which the kinetic energy of the particles is kept constant.

A synchrotron light source is a combination of different accelerator types, including a storage ring with beamlines and usually a synchrotron (which is sometimes called booster in this context). Synchrotron light sources in their entirety are sometimes called "synchrotrons", although this is technically incorrect.