Kilroy Was Here is the eleventh studio album by the American rock band Styx, released on February 22, 1983. A concept album and rock opera about a world where rock music is outlawed, it is named after a famous World War II graffiti tag, "Kilroy was here". It was the last album of original material to be released by the "classic" lineup of Dennis DeYoung, Tommy Shaw, James "J.Y." Young, John Panozzo, and Chuck Panozzo.

The album spawned two hit singles, the synth-pop "Mr. Roboto" which later became one of their signature songs, and the power ballad "Don't Let It End". Both of them were major hits in 1983, peaking at No. 3 and No. 6 respectively, on the US Billboard Hot 100.

The album is certified platinum by the RIAA. It is the most recent studio album by the band to be certified platinum.

In 2022, Rolling Stone named it one of the 50 Greatest Concept Albums of All Time.