Mindless Self Indulgence (often identified using the abbreviation MSI) is an American musical group formed in New York in 1997. Their music has a mixed style including punk rock, alternative rock, electronica, hip-hop, and industrial. Due to the style of their music lacking a definite genre, they coined the term 'Industrial Jungle Pussy Punk' to describe their music, but later, they denounced the term. Their group name is derived from a solo album that frontman Jimmy Urine self-recorded in the mid-1990s.

The group was formed when Urine was joined by fellow musicians Steve, Righ?, Vanessa Y.T. (who was later replaced by LynZ) and Kitty. They have released four albums, two EPs, one live album, and one live DVD. Rather than signing traditional record contracts, the band has licensed most of their albums to record labels, retaining ownership of the music.

The group maintains a devout fanbase, and has opened for many well-known acts such as Linkin Park, System of a Down, Korn, Sum 41, Insane Clown Posse and Rammstein. Notable bands who have opened for them include The Dresden Dolls, Rasputina, mc chris, The Birthday Massacre, Tub Ring, Fake Shark - Real Zombie! and Dog Fashion Disco.

In January 2009 the band headlined the Kerrang! Relentless Energy Drink tour, though LynZ did not participate due to her pregnancy.

In December 2010, they released a comic entitled 'Adventures Into Mindless Self Indulgence' about various tour stories and significant moments of the band's career.