Formerly a County Borough within the county of Hampshire (to which it gave its name, the County of Southampton or Southamptonshire - this was officially changed to Hampshire in 1959 though the county had been commonly known as Hampshire or Hantshire for centuries), it became a non-metropolitan district in 1974. However, the city became independent administratively from that county as it was made into a unitary authority in a local government re-organisation on 1 April 1997. The district remains part of the Hampshire ceremonial county.

The Liberal Democrats control the City Council.

There are three members of parliament for the city: Rt Hon John Denham (Labour) for Southampton Itchen (constituency for the east of the city), Dr Alan Whitehead (Labour) for Southampton Test (the west of the city), and Sandra Gidley (Liberal Democrat) for Romsey (which includes a portion of the north of the city).