Four Star Trek films were released in the 1980s.
The decade began with Star Trek II: The Wrath of Khan in 1982, followed by Star Trek III: The Search for Spock in 1984, Star Trek IV: The Voyage Home in 1986, and Star Trek V: The Final Frontier in 1989. The first film, Star Trek: The Motion Picture, premiered in 1979, so it is not part of the 1980s total.
The count can be confusing because Star Trek VI: The Undiscovered Country arrived in 1991, just outside the decade. These four films all feature the core Original Series cast, although the cast’s roles and the production styles changed across the run. The 1980s sequence also contains the franchise’s most tightly connected trilogy: The Voyage Home follows directly from The Search for Spock and concludes the Genesis-era storyline.