The 20 year old giant has impressed coach Des Hasler in three excellent trial displays to edge out Kevin McGuinness for a centre spot.
Stephenson played with the premiership winning Brisbane colts side last year after joining the Broncos from his hometown of Taree on the north coast of NSW.
He is one of 10 newcomers to the 18 from last season.
Players making their premiership debuts for the Sea Eagles on Saturday in addition to Stephenson include fullback Andrew Walker, winger Chris Hicks, five eighth Jye Mullane, halfback Michael Monaghan, props Daniel Heckenberg and Ian Donnelly, hooker Nathan Hollingsworth and bench forwards Kylie Leulluai, Nick Patterson and Shayne Dunley returns after a season at Parramatta.
Prop Jason King (shoulder) and centre Albert Torrens (suspension) weren't considered for selection while regular hooker Chad Randall hasn't played because of a groin operation and is still on the injured list.
The Manly side is: 1 - Andrew WALKER 2- Scott DONALD 3 - Luke WILLIAMSON 4 - Paul STEPHENSON 5 - Chris HICKS 6 - Jye MULLANE 7 - Michael MONAGHAN 8 - Ian DONNELLY 9 - Nathan HOLLINGSWORTH 10- Daniel HECKENBERG 11- Sam HARRIS 12 -Solomon HAUMONO 13 -Steve MENZIES (c)
Replacements: 14- Shayne DUNLEY 15 -Kylie LEULUAI 16 -Anthony WATMOUGH 17 -John HOPOATE 18 -Nick PATTERSON