Monmouth Battlefield State Park is a 1,818-acre (7.36 km2) New Jersey state park located on the border of Manalapan and Freehold Township, in Monmouth County, New Jersey, United States. This park preserves the historical battlefield on which the American Revolutionary War's Battle of Monmouth (1778) was waged. It was added to the National Register of Historic Places for its significance in military history.