Jordan Petaia, 19, is the only uncapped Australia player in Michael Cheika's squad for the showpiece event, which starts on September 20.
For the first time in over a year, George Ford and Owen Farrell will be in England's starting line-up when they face Ireland.
Ross Byrne will start Ireland's meeting with England at fly-half as Johnny Sexton and Joey Carbery struggle with injury.
MMA promotion Bellator has signed former England rugby union star James Haskell, who is expected to make his debut in 2020.