Irvine Luther Lenroot (January 31, 1869 - January 26, 1949) was a member of the United States Republican Party who served in the House of Representatives from 1909 - 1918, and in United States Senate from 1918 - 1927, for the state of Wisconsin.

Lenroot was born in Superior, Wisconsin in 1869 and began practicing law in 1898. He served as a member of the Wisconsin State Assembly from 1901 - 1907, and as Speaker of the Assembly from 1903 - 1907.

He became a senator in 1918 to fill the vacancy caused by the death of Paul O. Husting. He was elected in 1920. He ran for the Senate again in 1926, but lost. He was also Warren G. Harding's personal preference for vice president of the United States in 1920, but lost the nomination to Massachusetts Governor Calvin Coolidge.

He was appointed a judge of the United States Court of Customs and Patent Appeals by President Herbert Hoover in 1929, and served there until his retirement in 1944.

Lenroot is interred at the Greenwood Cemetery in Superior, Wisconsin.