Lost broadcast a total of 121 episodes over six seasons.
The ABC science-fiction drama premiered on September 22, 2004, and ended on May 23, 2010. Its 121-episode run follows the survivors of Oceanic Flight 815, whose crash strands them on a mysterious island filled with hidden societies, scientific experiments, and apparently supernatural forces.
The episode total can cause confusion because Lost often used two-part stories and extended broadcasts. The two-part finale, “The End,” is commonly counted as the 120th and 121st episodes overall, even though it was presented as a single extended television event in some listings. Similar counting differences affect certain season premieres and finales.
The six seasons were not equal in length. The first three generally followed the longer network-season format, while seasons four through six were shortened after the producers and ABC agreed on an end date. The final three seasons therefore had fewer episodes but were designed to move the overarching mythology toward its conclusion.