Stephen Crawford Young Jr. (born 11 December 1956) is a Scottish musician, and the rhythm guitarist and backing vocalist for the Australian rock & roll band AC/DC. He joined the band in April 2014, to record the group's Rock or Bust album, but was not announced as an official member of the band until September of that year. He replaced his uncle, Malcolm Young who retired due to dementia. He had previously filled in for Malcolm on AC/DC's 1988 US tour.