Retro Active is a compilation album by the English rock band Def Leppard, released in 1993. The album features touched-up versions of B-sides and previously unreleased recordings from the band's recording sessions from 1984 to 1993. The album charted at number 9 on the Billboard 200 and No. 6 on the UK Albums Chart.

After releasing only five albums over the course of a twelve-year period, Def Leppard used Retro Active to break that habit, provide a treat for diehard fans, and close the door on the "Steve Clark" era of the band. Many of the tracks had previously been released as single B-sides.

According to singer Joe Elliott, the concept behind the album was envisioned after the success of the "Two Steps Behind" single. The song had originally been demoed solely by Elliott as an electric version in 1989, and was subsequently recorded by the band as an acoustic ballad at the suggestion of guitarist Phil Collen. When the producers of the film Last Action Hero contacted the band in 1993 to provide a new song for the soundtrack, the band were unable to record new material due to touring schedules and instead sent over the multitrack tape of the acoustic version of "Two Steps Behind", which was given strings by conductor Michael Kamen in April 1993 and included onto the film soundtrack. It would become the band's last Top 20 single in the US, reaching No. 12, and inspired the band to put the album together and re-record the electric version of the song.

"She's Too Tough" and the electric version of "Miss You in a Heartbeat" were both B-sides included as bonus tracks on Japanese pressings of Adrenalize. Written in 1985, "She's Too Tough" first appeared on the Helix album Wild in the Streets in 1987. "Miss You in a Heartbeat", meanwhile, was first written and demoed by guitarist Collen in 1991 and was originally recorded by the Law, a band featuring Paul Rodgers and the Who drummer Kenney Jones, for their self-titled album in 1991. Def Leppard later recorded their own version in April the following year, which they released as a B-side on the "Make Love Like a Man" single. After the band had recorded the new vocal, bass and drum parts for the electric version of the song, Collen overheard Elliott experimenting with the song on a piano. This led Elliott to record a piano and vocal version of the song, after which Collen, bassist Rick Savage and drummer Rick Allen added acoustic and electric guitars, bass guitar and drum parts in June 1993, creating the acoustic version that would be released as a single.

Two unfinished songs from the Hysteria recording sessions, "Desert Song" and "Fractured Love", were completed exclusively for the album. The album also features several covers, namely Sweet's "Action" (which charted higher than the original in the UK) and Mick Ronson's "Only After Dark".

The version of "Ride into the Sun" on the compilation is not the same as that which appeared on The Def Leppard E.P., but rather the 1987 re-recording. It differs slightly from the original B-side from the Hysteria era; the B-side featured a Rick Allen drum solo intro, whereas the version on Retro Active has a piano intro provided by Ian Hunter.

Retro Active features a hidden (final) track: a piano/vocal version of "Miss You in a Heartbeat", which also features an alternate acoustic guitar solo by Collen.

This is the first Def Leppard album to feature songs recorded with newly added guitarist Vivian Campbell.