Hjalmar Petersen (January 2, 1890 – March 29, 1968) was an American politician who served as the 23rd Governor of Minnesota.

[2] After serving as Askov's village clerk and mayor, Petersen won two terms in the Minnesota House of Representatives,[3] where he sponsored the state income-tax law and urged that tax revenues be spent on public education.

He was sworn in as governor two days after Olson died of cancer on August 22, 1936.

He served the remainder of Olson's term but declined to run for governor himself in the November general election, opting instead to launch a successful bid for Railroad and Warehouse Commissioner, a position he then assumed after leaving the governorship on January 4, 1937.

[4] After his term as governor, he served as the president of the American Publishing Company.