Isildur cuts the One Ring from Sauron’s hand in J.R.R. Tolkien’s legendarium. This occurs at the end of the War of the Last Alliance, after Sauron has been defeated by the combined forces of Elves and Men.
Isildur uses the hilt-shard of his father Elendil’s sword, Narsil, to sever the Ring from Sauron. The act destroys Sauron’s physical form but does not destroy the Ring itself. Isildur then keeps the Ring instead of casting it into Mount Doom, allowing its evil influence to continue.
The scene is described in the prologue and histories associated with The Lord of the Rings. In the films, Elendil and Gil-galad also play crucial roles in the battle, but Isildur is the character who actually cuts off Sauron’s finger and takes the Ring.