8 is a lock and dam located near Genoa, Wisconsin on the Upper Mississippi River near river mile 679.2 in the United States.

It was constructed and was put into operation by April 1937.

The site underwent major rehabilitation from 1989 to 2003.

The lock and dam are owned and operated by the St. Paul District of the United States Army Corps of Engineers-Mississippi Valley Division.

The dam consists of a concrete structure 934 feet (284.7 m) long with five roller gates and 10 tainter gates.