Sentinels were giant robot mutant hunters created by Bolivar Trask.
Sentinels were first created by Bolivar Trask and Henry Peter Gyrich to track and capture mutants, in the hopes of ridding the world of them. It was a Sentinel that apparently killed the X-Man, Morph and managed to capture both Beast and Jubilee. The X-Men later recued Jubilee and destroyed the factory where the Sentinels were being produced. On Genosha, Sentinels were again being produced by Gyrich and Trask as well as the giant Sentinel, Master Mold. The Sentinels helped to capture mutants who visited the island nation but were again destroyed by the X-Men and Cable. Back in America, Master Mold gained control over the robots and ordered the to kill both mutants and humans. The Sentinels kidnapped Senator Kelly and but they were later destroyed by Charles Xavier and Magneto.
It was later revealed that Master Mold had survived the previous attack and it was beginning to manufacture Sentinels again. However, Morph, who was revealed to have survived his previous encounter with the robots, managed to destroy the Sentinels and Master Mold for good.
In an alternate future, the Sentinels managed to rule over a ruined Earth after Senator Kelly was assassinated by Mystique and the blame was put on all mutants. The Sentinels were dispatched to eliminate all mutants but they later turned against humans and ruled the world. Bishop managed to travel back in time and prevent the assassination from ever happening.