The 1918 United States Senate election in Minnesota took place on November 5, 1918. It was the first election for Minnesota's Class 2 seat in the United States Senate, and the second U.S. Senate election in Minnesota overall, held after the ratification of the Seventeenth Amendment to the United States Constitution, which established the popular election of United States Senators. Incumbent U.S. Senator Knute Nelson of the Republican Party of Minnesota easily defeated his challenger in the general election, Willis Greenleaf Calderwood of the National Party, to win a fourth term in the Senate.

Knute Nelson was a Norwegian-born American attorney and politician active in Wisconsin and Minnesota. A Republican, he served in state and national positions: he was elected to the Wisconsin and Minnesota legislatures and to the U.S. House of Representatives and the United States Senate from Minnesota, and served as the 12th governor of Minnesota from 1893 to 1895. Having served in the Senate for 28 years, 55 days, he is the longest-serving Senator in Minnesota's history.