Bernhard Berthelsen (16 March 1897 - 25 August 1964) was a Norwegian politician for the Liberal Party.
Berthelsen was born in Sør-Audnedal. He was elected to the Norwegian Parliament from the Market towns of Telemark and Aust-Agder counties in 1945, and was re-elected on one occasion.
Berthelsen was a deputy member of the executive committee of Arendal city council from 1934 to 1940. He then sat as a regular city council member in the periods 1940 - 1944 and 1945 - 1946. He was later a member of Bergen city council during the term 1955 - 1959.