Niels Arntzen Sem (10 February 1782 – 19 December 1859) was a Norwegian politician.

He was elected to the Norwegian Parliament in 1825 and 1827, representing the constituency of Stavanger Amt.

[3] While working in Buskerud, he was elected to the Norwegian Parliament to represent that county in 1830.

He then served as Diocesan Governor of Christianssand stiftamt as well as County Governor of Lister og Mandals amt (one of its subordinate counties).

[3] From October 1852 until 12 April 1853 he was an acting member of the Council of State Division in interim in Stockholm, founded during King Oscar I's illness.