"Holy Wars... The Punishment Due" is the opening track of heavy metal band Megadeth's 1990 album Rust in Peace.
The song has an unusual structure, shifting at 2:26 after an acoustic bridge by Marty Friedman to a different, slower and heavier section called "The Punishment Due", before speeding up again. The entire song is commonly referred to as simply "Holy Wars".
The lyrical theme of "Holy Wars" deals with the Northern Ireland conflict, and Mustaine's feelings concerning religion. In an interview with the UK magazine Guitarist, Mustaine says that he was inspired to write the song in Northern Ireland, when he discovered bootlegged Megadeth T-shirts were on sale and was dissuaded from taking action to have them removed on the basis that they were part of fund raising activities for "The Cause" (i.e. the Provisional Irish Republican Army). Dave also stated at a gig at Rock City (Nottingham, U.K. 18 February 2008) that it was at this venue that he wrote Holy Wars, after they travelled there from Ireland in a bulletproof bus. "The Punishment Due" is based on the popular Marvel comic book character, The Punisher.
A cover version of the song is playable in the band simulation game Rock Revolution. The master recording is purchasable as part of the Rust in Peace album pack on the Rock Band band simulation platform, and is also playable in the Guitar Hero: Warriors of Rock game.