Frank Steunenberg (August 8, 1861–December 30, 1905) was the governor of the U.S. state of Idaho from 1897 until 1901.

He was elected in 1896 as a candidate of both the Populist Party and the Democratic Party, and with the support of labor unions. As a result, many corporations, fearing that Steunenberg's government would not support them if there was a strike, increased their wages for workers.

The Bunker Hill Company , however, did not, and the miners working for that company went on strike. Steunenberg ignored his campaign promises and sent out the militia to crush the strike. He did not run for reelection in 1900.

On December 30, 1905, he was assassinated outside his house. Big Bill Haywood and two other labor leaders, Charles Moyer and George Pettibone , were tried for authorizing the murder. The trial, which received national attention, resulted in them being acquitted. It is most likely that Steunenberg was in fact killed by a labor union sympathizer angry because he betrayed the unions while he was governor.