The crash occurred at 12:56 p.m. Saturday 1 mile east of Mercer on Highway 200.
The patrol said a 42-year-old Mandan man was driving a 2001 Harley-Davidson with the 40-year-old Mandan woman as his passenger. The two were part of a group of motorcycles traveling eastbound on the highway when a deer struck the 2001 Harley-Davidson, causing the driver to lose control. The driver was thrown into the ditch and the woman passenger on the roadway. The passenger was then struck by a 2012 Harley-Davidson.
The driver and passenger of the 2001 Harley-Davidson were transported to CHI-St. Alexius in Turtle Lake, N.D., where the woman was pronounced dead, the patrol said.
The driver of the 2001 Harley-Davidson was airlifted to CHI-St. Alexius in Bismarck for treatment of serious injuries.
The driver of the 2012 Harley-Davidson was not injured.
The crash is under investigation.