Walter Duncan McIndoe (March 30, 1819 – August 22, 1872) was a lumber industrialist and politician from north-central Wisconsin. Among his notable achievements was election to the United States House of Representatives.
Born in Dumbartonshire, Scotland, McIndoe immigrated to the United States in 1834. He engaged in business in New York, Charleston, and St. Louis, finally settling in Wisconsin in 1845 where he became involved in the lumber business. He served as a member of the Wisconsin State Assembly in 1850, 1854, and 1855. In 1850 as a member of the Assembly he introduced a bill changing the name of his home community from Big Bull Falls to Wausau and creating Marathon County. Initially a Whig, in 1854 he became a member of the newly formed Republican Party. At the 1857 Republican Party convention, he was a gubernatorial candidate, contending with Edward Dwight Holton, with both candidates losing to the eventual governor, Alexander Randall. During the Civil War he was provost marshal of Wisconsin.
McIndoe was elected as a Republican to represent Wisconsin's 2nd congressional district in the Thirty-seventh Congress to fill the vacancy caused by the death of Luther Hanchett (January 26, 1863–March 3, 1863). He was reelected to the Thirty-eighth and Thirty-ninth Congresses this time as the representative of Wisconsin's newly created 6th district serving from March 4, 1863 to March 3, 1867. During the Thirty-ninth Congress, he served as chairman of the Committee on Revolutionary Pensions. In 1866, McIndoe declined candidacy for renomination, instead resuming his interests in the lumber business. He died in Wausau, Wisconsin on August 22, 1872 and was interred at Pine Grove Cemetery.