Parliament House, on the corner of North Terrace and King William Road in the Adelaide city centre, is the seat of the Parliament of South Australia. It was built to replace the adjacent and overcrowded Parliament House, now referred to as "Old Parliament House". Due to financial constraints, the current Parliament House was constructed in stages over 65 years from 1874 to 1939.

Guided public tours of the building are held on weekdays at 10am and 2pm, except when the Parliament is sitting.

The Parliament of South Australia began in 1857, when the colony of South Australia was granted self-government.

Old Parliament House on North Terrace is situated to the west of the new Parliament House, and is associated with numerous and progressive legislative reforms in which South Australia led the way (such as the introduction of full adult male suffrage in 1856, and women's suffrage in 1894). The building, designed over many stages, incorporates the work of three important colonial architects: William Bennett Hays; Edward Angus Hamilton (both of whom held the office of Colonial Architect of South Australia); and Edward John Woods. Originally built as a single room brick chamber in 1843, the building was then extended in 1857 to accommodate the new bicameral Parliament. Sandstone used in the construction of the building included the quarried rock of the sacred Kaurna site called "Tarna Kanya" (meaning the Red Kangaroo Rock) on the River Torrens/Karrawirra Pari. The use of this stone has been described as the "wholesale destruction of one of the Kaurna's most important sacred sites".

It is one of only a few buildings constructed before 1860 remaining in Adelaide.

Following the completion of the new Parliament House in 1939, Premier Thomas Playford proposed that the old complex be demolished. It was saved by the onset of the Second World War and its use as a Royal Australian Air Force recruiting office. Thereafter it was used by government departments.

Further modifications and alterations continued through to the 1970s, but by the mid-1970s the complex was sadly run down and neglected. In the late 1970s it was converted to the "Constitutional Museum" and was restored to reflect its 1875 condition. Under the direction of the newly created History Trust of South Australia, the museum (Australia’s first political museum) operated under that name from 1979, and then as "Old Parliament House" until 1995. The building then reverted to use by the parliament, largely as offices and committee rooms.

In 1872 legislation increased the House of Assembly by 10 members, effective from 1875, reflecting the increased colonial population. It was decided that a completely new building was needed for the expanding parliament. A commission, appointed by the Governor of South Australia, was set up in 1874 to adjudicate a design competition for the new building that would form the basis of ‘New’ Parliament House. A design by prominent Adelaide architect Edmund Wright and his partner Lloyd Taylor was selected as the winner. This Greek Revival design featured ornate columns of the Corinthian order, impressive towers, and a grand dome.