29-year-old Bateman made 73 appearances for the Ospreys between 2003 and the end of last season and figured in the 2006 triumph over Australia.
He will link up with former Ospreys teammate Lee Beach in the Neath pack and the latter is set to lead the Welsh All Blacks’ bid to win the title for a fifth successive season.
Also returning to The Gnoll is Pontypridd back row man Lee Evans, who played for Neath at U21 level before joining the Sardis Road club in 2003, while Ebbw Vale’s Neil Edwards is also heading to the home of the champions.
Wales U18 outside half Matthew Jarvis has also pledged his future to Neath from next season.
