The Sentinels were recurring foes of the X-Men in the X-Men 1990's cartoon series. Created by Bolivar Trask under the direction of Henry Gyrich of the Mutant Control Agency, the Sentinels were supposed to act as defenders of humanity by targeting and apprehending mutants. The President of the United States had called for a shutdown of the Sentinel Project, but the bigoted Gyrich continued the project despite the President's order.
After an encounter with a Sentinel robot at a shopping mall, the X-Men mobilised to deal with the threat. They destroyed the mutant registration files at the MCA head office and demolished the Sentinel factory, but Gyrich and Trask later moved their operation to the island of Genosha. Their, they constructed Master Mold and attempted to lure mutants to Genosha under the pretence that it was a mutant-friendly vacation resort. Mutants who arrived there were enslaved and their powers surpressed while they were forced to work on constructing a hydroelectric plant to suit Master Mold's mass-production needs. The X-Men later caught wind of this scheme and destroyed the facility, but Master Mold survived and repaired itself.
Master Mold came to the realisation that mutants could never be eradicated unless the human population was controlled, and so its Sentinel forces abducted US senator Robert Kelly in order to replace his brain with a computer so that Master Mold could use him to infiltrate the American government. The Sentinels also attempted to abduct mutant terrorist Magneto, but he was able to escape from them and informed the X-Men. The X-Men then raided Genosha, battling a fleet of Sentinels and destroying Master Mold, seemingly ending the Sentinel threat once and for all.