X is an Australian punk rock band, formed in Sydney in 1977 and led by the late Ian Rilen. The band has split and reformed several times.
Although X has had several members, its sound has been defined by two distinctive elements: Rilen's basslines and Steve Lucas's guitar. Drummer Cathy Green has also been a frequent member of the band since 1984.
Rilen was also a founding member of bluesy hard rockers Rose Tattoo. During X's first hiatus (1980–83), he formed the post punk outfit Sardine v, with his then wife, Stephanie Rilen. As of 2004, Rilen had settled on a fairly stable line up of his current project, Ian Rilen & the Love Addicts, who included Cathy Green on bass. The band have also issued a CD, "Passion Boots & Bruises."