Desmond David Hume is a fictional character on the ABC television series Lost portrayed by Henry Ian Cusick. Desmond's name is a tribute to David Hume, the famous empiricist philosopher. Desmond was not a passenger of Flight 815. He had been stranded on the island three years prior to the crash as the result of a shipwreck. Desmond eventually leaves the Island with the Oceanic 6 and is reunited with his love Penny Widmore (Sonya Walger).

It appears that Desmond was the "package" that Charles Widmore (Alan Dale) was talking about on Hydra Island. It was later revealed by Charles Widmore that Desmond was Jacob's "fail-safe", meaning that in case the Man in Black killed all of Jacob's candidates, Desmond would then be used to destroy the island.

Desmond was one of the show's most popular characters. In 2006, Cusick's portrayal was nominated for an Emmy. In 2007, a two-week-long tournament-style competition for Lost's best character, with over 6,000 voters, hosted by The Washington Post voted Desmond the winner.