Riksdag, national parliament of Sweden, formed in 1866. Originally a two-chamber legislature, it became a single chamber body in 1971. Representation in the chamber is proportional. Members are elected by universal suffrage for a term of three years. The cabinet is responsible to the Riksdag. A new constitution, effective in Jan., 1975, which eliminated the monarch's residual authority, gave the speaker of the Riksdag rather than the king the right to appoint a new premier.

The Riksdag is the official Swedish term of the Parliament of Sweden and the Parliament of Finland (in Finland alongside the Finnish word eduskunta). In Swedish, the word has also become commonly used as a generally term for a legislative assembly, a parliament (parlament).

The word Riksdag derives from the Swedish term Riksens ständer ("the Estates of the Realm"). It refers to a meeting of representatives from across Sweden and has been used in Sweden since the Middle Ages. With the introduction of the bi-cameral legislative assembly in 1866, the term Riksens ständer was officially changed to Riksdag.

In Finland, the earlier Swedish term for the parliament, Lantdag, was changed to Riksdag in the new republican constitution in 1919.

Riskdag has cognates in the German word Reichstag (used for various German national parliaments up until 1945), the Danish rigsdag (used for the parliament of Denmark 1849-1953) and the Estonian riigikogu (used for the parliament of Estonia 1920-1940 and again since 1991).