Def FX, fronted by media darling and practicing Wiccan Fiona Horne and visual artist Sean Lowry, are an electronic-metal-pop group from Australia. The band were active from 1990 till their dissolution in 1997.

They toured extensively and released several critically-acclaimed EPs on independent label Phantom Records (later collected together on the album Baptism) before their 1992 album debut, Light Speed Collision on EMI, which featured the singles Space Time Disco and No Time for Nowhere. In 1994, their final release for EMI, Post Moronic EP featuring the Triple J hit Masses Like Asses, became their first charting CD, reaching No.43 on the weekly ARIA charts. EMI then released them from their contract and gave them the full rights to all of their EMI material.

During 1995, the band started their own label on which they rereleased most of their old material as well as the album Ritual Eternal, which featured many themes from Fiona's Wiccan religion as well as Indian mythology. They followed this up in November with the EP Psychoactive Summer, featuring live versions of several Ritual Eternal songs. The track, at the more pop end of their range, was an instant hit on both Triple J and commercial stations.

In 1996 they released their final and by far most successful album, Magick, featuring Psychoactive Summer and Spell On You. It integrated more pop and electronica into their sound than any of their previous releases. However, in May 1997, Lowry left unexpectedly and the remaining members decided to dissolve the band. Fiona wrote and released a book about Wicca while some of the others formed the band Primary.