Insomniac is the fourth studio album from the punk rock band Green Day. It was released in 1995 on October 10, through the Reprise Records label. Though it reached #2 in the U.S. and went double Platinum, Insomniac did not have the sales endurance of its predecessor, Dookie, largely due to its slightly darker lyrical tone and more abrasive sound . Though many consider Insomniac to be more consistent than Dookie, it did not feature a well-known hit single akin to "Longview" or "Basket Case" from Dookie or "Good Riddance (Time of Your Life)" from Nimrod. Before the name 'Insomniac', the band considered the naming the album 'Tight Wad Hill' (after the thirteenth track of the album). After visiting collage artist Winston Smith for the album cover, Billie Joe Armstrong asked him how he managed to make such intricate pieces in such short times. Smith answered, "It's easy for me. I am an insomniac." Insomniac has sold 2 million units in the United States as of August 2006. It is Green Day's third biggest selling album after Dookie and American Idiot.

It is sometimes compared to Seattle grunge band Nirvana's third and final album, In Utero. Nirvana brokethrough with Nevermind and then followed it up with a more challenging release, designed to eliminate some of the audience. Green Day's Insomniac is a similar situation. Dookie made the band big huge multi-platinum superstars, and Insomniac saw the band venture into a less radio friendly more abrasive sound.