The Flatrock River, also known as Flatrock Creek and other variants of the two names,[2] is a 98-mile-long (158 km)[3] tributary of the East Fork of the White River in east-central Indiana in the United States.

[5] The Flatrock River rises near Mooreland in northeastern Henry County, and flows generally southwestwardly through Rush, Decatur, Shelby and Bartholomew counties, past the communities of Lewisville, Rushville and St. Paul.

In Decatur County it collects the Little Flatrock River,[7] which rises in Rush County and flows southwestwardly 23.4 miles (37.7 km),[3] past Milroy.

[6] The United States Board on Geographic Names settled on "Flat Rock River" as the stream's name in 1917, and changed it to "Flatrock River" in 1959.

According to the Geographic Names Information System, it has also been known historically as "Big Flat Rock River," "Big Flatrock River," "Flat Rock Creek," and "Flatrock Creek.