Mose Masoe will leave St Helens at the end of the season to return to the NRL.
The 25 year-old Samoan has confirmed he will join St George Illawara Dragons on a two-year deal.
The giant prop forward joined Saints from Penrith Panthers for the 2014 season.
Since his debut in March last year, Masoe has featured in every 19-man squad for the reigning Super League champions.
“We’re sad to be losing Mose as he has been a popular member of the squad and at the hub of a pack,” Saints head coach Keiron Cunningham told BBC Sport.
“He is a really good bloke who I know will want to end his Saints career with more winner’s medals.”
Peter Mullholland, Dragons Director of Recruitment and Retention told the St George club website:
“Mose will be a welcome addition to the Club as he is able to provide both the additional size and go-forward which is vital in all strong forward-packs.
“He is presently playing his trade in the traditionally-physical Super League competition and is a key player for the strong St Helens club.
“We look forward to welcoming him to the Club during the off-season.”