Police Academy 4: Citizens on Patrol is a 1987 American comedy film. It is the fourth installment in the Police Academy franchise. It was released on April 3, 1987, and is the sequel to Police Academy 3: Back in Training (1986).

A group of Police Academy graduates are sent to train a group of newly recruited civilian officers. The original Police Academy cast reprise their roles in the film. Capt. Thaddeus Harris (G. W. Bailey), not seen since the first installment, returns as the film's nemesis. In Police Academy 2 and 3, Capt./Commandant Ernie Mauser (played by Art Metrano) filled that role, but Metrano asked to be replaced for the remainder of the series after filming the third film. This was the last Police Academy film to feature Steve Guttenberg as Carey Mahoney. This film also stars a young David Spade in his feature film debut, as well as featuring a brief appearance from pro skateboarder Tony Hawk as Spade's double in a skateboarding scene. The film was a commercial success, but was panned by film critics. It was followed by Police Academy 5: Assignment Miami Beach (1988).

Commandant Eric Lassard decides the police force is overworked and understaffed, so he comes up with the idea of recruiting civilian volunteers to work side by side with his officers in a program called "Citizens On Patrol" (COP).

Carey Mahoney and his friends Moses Hightower, Larvell Jones, Eugene Tackleberry, Zed McGlunk, Carl Sweetchuck, Laverne Hooks, and Debbie Callahan are in charge of training the civilians. The civilians include the enormous Tommy "House" Conklin (who Hightower used to babysit), gung-ho senior citizen Lois Feldman, Tackleberry's own father-in-law Mr. Kirkland, and skateboarding delinquents Kyle Rumford and Arnie Lewis. The latter pair were caught by Captain Thaddeus Harris, and the judge was about to throw the book at them until Mahoney speaks to the judge to let Arnie and Kyle join the COP program as alternative punishment. The judge agrees, and the boys are joined by their attorney, Milt Butterworth.

Believing "the concept of citizens doing police work is asinine", Harris is determined to see the COP program fail and take over Lassard's job at the academy. When Lassard leaves on an overseas conference, Harris, and his right-hand man Lt. Carl Proctor, are put in charge of the academy and Harris immediately plots to make the COP volunteers quit and leave police work to officers.

The volunteers, however, do well in their training. Mrs. Feldman excels in firing Tackleberry's .44 Magnum, and they bond amicably (she reminds him of his mother). In training in water safety and drowning victim rescue, Zed rescues a cadet and gains a love interest, a reporter/photographer Laura, who has come to view Lassard's COP program and becomes attracted to Zed. Unfortunately, Harris ruins the moment, insulting them both and inspiring Zed to replace Harris' deodorant with mace, which burns his armpits. Despite pranks pulled on him during training, Harris is still determined to make the Citizens on Patrol program fail.

Jones learns that volunteers House, Kyle and Arnie feel ready to go out and arrest criminals, so he, Mahoney, Hightower, and Tackleberry prank the boys, locking them in a prisoner transport van with Hightower, who is posing as a Voodoo practitioner who reanimates Tackleberry's "dead" brother, as a Jason Voorhees-esque maniac with a chainsaw to make them take training more seriously. Later, after Harris yells at Zed again, calling him a disgrace, Laura comforts him, saying she thinks he is perfect.

After COP volunteers accidentally foil an undercover police sting, the program is suspended, much to Harris' delight. Mahoney believes he did it on purpose to shut down the COP program, paying him back by putting superglue on the mouthpiece of Harris' bullhorn, semi-permanently sticking the mouth guard to its rims. Sometime later, Harris gives some prominent citizens a tour of his precinct when Proctor is tricked into releasing every inmate at the precinct 19 jail, including a team of ninjas and Randall "Tex" Cobb. After the criminals imprison Harris and his guests, they escape into the street, only to run into Mrs. Feldman, who immediately informs the Lassard academy.