Murder in Small Town X (sometimes abbreviated MiSTX) is an American reality television series created by George Verschoor, Robert Fisher Jr., and Gordon Cassidy and was hosted by Sgt. Gary Fredo, a California Police Investigator, that aired on Fox from July through September 2001. The series immerses contestants in a fictional town, and challenges them to solve a murder. Each week, one of the contestants is "murdered" (and removed from the show); the final contestant solves the case and wins $250,000.

Although classified as a reality television series, given the format's unique nature, it was more accurately described as a hybrid of a reality TV show, game show, and mystery drama. It is notable for the fact that its winner, New York City fireman Ángel Juarbe Jr., was a first responder who died in the line of duty during the September 11 attacks, exactly one week after the show's finale aired.

The premise of the show was to bring 10 contestants from around the United States of America to the small fishing village of Eastport, Maine (called "Sunrise" in the show) to act as amateur investigators to solve a series of fictional murders.

Initially, the investigators were given a list of 15 suspects who were "townspeople" played by actors and actresses. A large number of improvisational actors and actresses were stationed around the real-life town, and their job was to provide clues (useful and not useful) to the investigators. Each week, the investigators were sent out on varying missions around the town in order to discover clues to clear suspects. Additionally, the murderer would strike again, clearing suspects as well.

In every episode a Lead Investigator, or Lifeguard, is chosen. In the first episode, the Lifeguard was chosen by random draw. For the following episodes, the Lifeguard is chosen by the investigator who was eliminated the previous episode via pre-recorded message. For the final two investigators, the previous investigator who was eliminated will determine who gets his or her first choice on which suspect they want to pursue.

Every three days, two envelopes, red and black, would be discovered somewhere in the town. In the red envelope, there would be a question about what the investigators had learned during the day. The question would usually be pointed to one of the track teams, meaning whoever was involved with that line of investigation has the highest potential of answering it correctly. The team's answer would be sent to the killer via e-mail, with the address being anonymous. If correct, the killer would clear one of the remaining suspects. If wrong, the number of suspects would remain the same.

Afterward, the black envelope would be opened. It contains two smaller black envelopes, each containing a map of a certain location. The investigators (except the Lifeguard) would go into a separate room to vote for the first person who will play the Killer's game. After the vote, the Lifeguard picks the second person who will play. The two investigators would each choose a map and head out to the two different remote locations completely alone, with their movements recorded only by night-vision cameras. One of the investigators would discover an important clue to the mystery, whereas the other would be eliminated off the show by being "murdered by the killer", with their last seconds seen through the eyes of said "killer" in the manner of classical slasher films.

Taco Bell promoted the show.