Several people and places are named Dahlgren.
Rear Admiral John A. Dahlgren (1809-1870) was a U.S. Navy officer noted for the weapons he designed.
Several places in the United States are named for him, including:
- Dahlgren, Illinois
- Dahlgren, Virginia, and the U.S. Naval base there, which was originally used for testing guns but is now more involved in the Space Program
- Dahlgren Hall at the U.S. Naval Academy in Annapolis, Maryland