Adam Frederik Oluf Arndtsen (15 December 1829 – 7 August 1919) was a Norwegian physicist.
Arndtsen was born in Alstahaug in Nordland, Norway. He studied at the Royal Frederick University (now University of Oslo). In 1859 he lost out to Hartvig Caspar Christie in a competition to succeed Lorentz Christian Langberg as an academic of physics at Royal Frederick University. He later became the first director of the Norwegian Metrology Service, serving from 1875 to 1914. From 1900 to 1914 he also represented Norway in the International Bureau of Weights and Measures.