Hennen is an Irish surname. Notable people with the surname include:
Bernhard Hennen (born 1966), German writer Pat Hennen (born 1953), American motorcycle road racer Stephan Hennen (born 1990), German footballer Thomas J. Hennen (astronaut) (born 1952), United States Army warrant officer and astronaut Thomas J. Hennen (bishop) (born 1978), American Catholic priest who is Bishop-elect of the Diocese of Baker