Charles Eugene Flandrau (July 15, 1828 – September 9, 1903) was an American lawyer who became influential in the Minnesota Territory, and later state, after moving there in 1853 from New York City. He served on the Minnesota Territorial Council, in the Minnesota Constitutional Convention, and on the Minnesota territorial and state supreme courts. He was also an associate justice on the Minnesota Supreme Court.
During the Dakota War, Flandrau enlisted in the Union Army and was commissioned as a captain in 1862 to raise a force to defend settlers at New Ulm. Given his success, the governor appointed him to lead the defense of southwest Minnesota, at the rank of colonel. After unsuccessfully campaigning for a couple of positions, Flandrau moved in 1870 to St. Paul, where he had a law partnership with two men until his death in 1903.