Otto Bahr Halvorsen (1872–May 23, 1923) was a Norwegian politician from the Conservative Party. He was Prime Minister of Norway from 1920 to 1921 and in 1923.

|- style="text-align: center;" | width="30%" |Preceded by:
Otto Blehr | width="40%" style="text-align: center;" |Prime Minister of Norway
1923 | width="30%" |Succeeded by:
Abraham Berge