There are four Lethal Weapon films in the main franchise. The series comprises:

• Lethal Weapon (1987)
• Lethal Weapon 2 (1989)
• Lethal Weapon 3 (1992)
• Lethal Weapon 4 (1998)

Context notes:

• A television series based on the franchise aired from 2016 to 2019, but it is distinct from the film lineup and is not counted as part of the four-film film series. If you’d like, I can also summarize the TV series and its relationship to the films.