Niels Onstad (1909 – 17 June 1978) was a Norwegian shipowner and art collector.
Niels Onstad was born in Kristiania in 1909. In 1935, together with his brother Haakon Onstad, he started the shipping company, Niels Onstad Tank Rederi A / S, which later was named Niels Onstads Tankrederi with headquarters in Oslo. Haakon Onstad had entered ship owning in 1932 with the Pan Gothia but because of the uncertain financial times the ship was given Swedish registry under Rederi A/B Pagota. In 1940, Niels Onstad fled to the United States during the Occupation of Norway by Nazi Germany.
Haakon Onstad relocated to Kungsbacka, Sweden where he formed Rederi A/B Kungsoil and Rederi A/B Monacus. In 1956 Niels Onstad married Sonja Henie. Onstad, whose mother had been a painter, had many contacts in the Norwegian art world, including Edvard Munch. Together, Onstad and Henie established the Henie Onstad Kunstsenter at Høvikodden in Bærum southwest of Oslo. Onstad played football for SFK Lyn in his younger days. He played as defender on the club's first-team, including a feature in the 1928 Norwegian Football Cup final.