In what year did Lost premiere?

Lost premiered in 2004, with its first episode airing on ABC on September 22 of that year.

The series begins after Oceanic Flight 815 breaks apart over the Pacific, leaving 48 survivors stranded on a mysterious island. The two-part pilot introduced the show's central ensemble, including Jack Shephard, Kate Austen, James “Sawyer” Ford, and Hugo “Hurley” Reyes. The second half of the pilot aired one week later, on September 29, 2004.

Lost was created by Jeffrey Lieber, J. J. Abrams, and Damon Lindelof. Its first season combined survival drama, flashbacks, science fiction, and supernatural mystery. The unusually expensive pilot helped establish the show's cinematic scale, while its strong premiere audience made it one of ABC's major successes of the 2004 television season.

A common mix-up is confusing the series premiere with the pilot's earlier world premiere at San Diego Comic-Con in July 2004. The broadcast premiere was in September, and the show ultimately ran for six seasons, ending in 2010.