An equatorial room, in astronomical observatories, is the room which contains an equatorial mounted telescope. It is usually referred to in observatory buildings that contain more than one type of instrument: for example buildings with an "equatorial room" containing an equatorial telescope and a "transit room" containing a transit telescope.^[1] Equatorial rooms tend to be large circular rooms to accommodate all the range of motion of a long telescope on an equatorial mount and are usually topped with a dome to keep out the weather.

In some cases an observatory would move to a new location, or the equatorial telescope itself would be removed. The space would then be converted, for example, into use as a classroom or library. These peculiar rooms can sometimes be found in buildings at old colleges and towns, with their former use long forgotten.