The Butterfly Effect is the fourth studio album by Portuguese gothic metal band Moonspell, released in 1999, inspired by chaos theory.

The album is characterised by a more experimental approach than their previous material, incorporating many elements of electronic music and industrial metal.

The music is composed primarily by the band's keyboardist, Pedro Paixão.

"Tired" samples Mozart's Requiem.

All lyrics are written by Fernando Ribeiro This 1990s metal album–related article is a stub.