The Massachusetts State Police (MSP) is an agency of the Commonwealth of Massachusetts' Executive Office of Public Safety and Security, responsible for law enforcement and vehicle regulation across the state. The MSP is known in the common local vernacular as The Staties, whose officers are referred to as Staties. As of 2024, it has 2,500 sworn troopers and 611 civilian support staff for a total of 3,111 personnel, making it the largest law enforcement agency in New England. The MSP is headed by Colonel Geoffrey Noble, the first colonel to not come from State Police ranks.

The MSP was established by Massachusetts state governor John A. Andrew when he signed a law creating the State Constabulary on May 16, 1865. This legislative act to "establish a State Police Force" founded the first statewide enforcement agency in the nation. The first leader of the State Police was William Sterling King, an American officer in the Union Army during the American Civil War. The agency remained small and rather informal until 1921, when the MSP was enlarged to comprise 50 officers stationed in barracks across the state with the primary mission of providing law enforcement to rural areas underserved by existing local police agencies. This law enforcement mission was performed by the trooper on horseback, usually, and in motor cars in areas with upgraded roads. The MSP enlarged its mission to handle primary vehicular regulation on the Commonwealth's interstate and limited-access highways after their development mid-century; during this period, it also established a presence in protecting Logan International Airport.

For much of the 20th century, the MSP was organized along military lines with a heavy emphasis on the role of the barracks, spartan working conditions, and a uniformity in appearance and internal culture. Until recently, the MSP maintained one of the strictest regimens for physical size requirements for applicants. Efforts are being made presently to render the department more racially diverse, as well as more inclusive of women and LGBT troopers.

Since its inception, 47 officers from the Massachusetts State Police and its former agencies which made up its ranks have been killed in the line of duty. The earliest death was in 1909 and the latest death was March 3, 2022.

In November 2019, Superintendent Gilpin announced her retirement as colonel of the Massachusetts State police after two years in the position.

During the 1960s and 1970s, the MSP issued the Walther PPK as a special assignment weapon.

During the 1980s, the .357 Magnum Smith & Wesson Model 65 was issued to the troopers. Different weapons were issued for off-duty and special assignments. Prior to 1986, they were issued two Smith & Wesson Model 65 revolvers, one with a 4 inch barrel for on duty wear, and one with a 3 inch barrel for off duty wear, they were required to wear a 3 inch barreled revolver even if they were at the beach in a bathing suit. They were required at the time to carry two weapons at all times, because they were considered one duty 24/7. From 1986 and on, the new off duty weapon was the .38 Special Smith & Wesson Bodyguard revolver.

The agency issued the SIG Sauer P226 in 9mm from the early 1990s, followed by the SIG Sauer P226 DAK (Double Action Kellerman) in .40 S&W.