Bernhard Martin Jacobsen (March 26, 1862 – June 30, 1936) was a Democratic U.S. Representative from Iowa who served nearly three full terms during the Great Depression.

Born in Tønder, (which was then a part of the Danish fief Schleswig, but is now in Denmark proper), Jacobsen attended the public schools.

In 1930, Jacobsen was elected as a Democrat to represent Iowa's 2nd congressional district, unseating incumbent Republican Congressman F. Dickinson Letts.

In the next two elections (in which Iowa Democrats established, then retained, a clear majority of U.S. House seats), Jacobsen won by large margins.

On June 1, 1936, Jacobsen won the Democratic primary for a fourth term, this time to the Seventy-fifth Congress.