Sivert Andreas Nielsen (24 November 1916 – 17 March 2004) was a Norwegian diplomat, civil servant, state secretary and banker.
He was born in Copenhagen as a son of professor Konrad Nielsen (1875–1953) and his wife Gudrun Agnes Augusta Müller (1889–1954).
He was imprisoned at Møllergata 19 from 2 April to 28 June 1941, and then in Grini concentration camp until 15 November.
In the latter position he was a part of the third cabinet Gerhardsen; however he was not a member of the Norwegian Labour Party.
He was decorated as a Knight of the Royal Norwegian Order of St. Olav in 1964, and died in March 2004 in Oslo.