Willard Decker was the Starfleet officer who oversaw the refit of the Enterprise and gave up his life by merging with V'Ger in Star Trek: The Motion Picture.
Willard Decker was a Starfleet commander who had overseen the refit of the Enterprise and was set to be its captain. When the vast entity V'Ger approached Earth, Admiral James T. Kirk used the emergency to take command himself, demoting Decker to executive officer and science officer. Decker resented the move but served loyally and often challenged Kirk's unfamiliarity with the redesigned ship.
Years earlier Decker had been posted on Delta IV, where he had a romance with the Deltan Ilia. When V'Ger took Ilia and replaced her with a probe in her form, Decker tried to reach the memories of the real woman inside the copy. At the heart of V'Ger, the crew learned it was a machine that wanted to join with its creator. Decker chose to merge with V'Ger and the Ilia probe, creating a new form of life, and was listed as missing.
Decker's sacrifice resolved the crisis of the first Star Trek film and gave a new direction to V'Ger's search for meaning.