Tour captain Sam Warburton has been rested following a knock to his knee received in training and O'Connell is one of six former Lions in the squad. He joins Adam Jones, Mike Phillips, Jamie Roberts, Alun Wyn Jones and Jamie Heaslip, all of who played in the opening game four years ago.
"I'm really excited by the first selection of the tour. Naturally it comprises largely those players not involved in last weekend's Aviva Premiership and RaboDirect PRO12 finals and we've a lot of players making their debuts for the Lions," said Gatland.
"At the same time we have a hard core of experience with the six former Lions sharing 430 caps between them and 19 Lions Tests. There are also some proven combinations such as the Welsh centre pairing and back row.
"Some of the boys who played last weekend are on the bench as cover and generally everyone in the camp is raring to go."
The game at the Hong Kong Stadium will be the first the Lions have played in Asia and the second against the Barbarians. The two teams last met at Twickenham Stadium in 1977, a game which was won by a Lions side containing current tour manager Andy Irvine and Barbarinas team manager Derek Quinnell.
"After all the pre-tour preparation in Cardiff and Dublin the match against the Barbarians on Saturday marks another milestone in the proud history of the Lions and the start of the 2013 tour," said Irvine.
"This is the important first match of a 10-match tour and the players are eager to get the tour off on the right note. Training has gone very well and it is exciting to see 11 players making their run-on debuts for the Lions, including the tour's youngest player Stuart Hogg."
British & Irish Lions (v Barbarians, 1 June, Hong Kong Stadium)
15. Stuart Hogg (Glasgow Warriors/Scotland)
14. Alex Cuthbert (Cardiff Blues/Wales)
13. Jonathan Davies (Scarlets/Wales)
12. Jamie Roberts (Cardiff Blues/Wales)
11. Sean Maitland (Glasgow Warriors/Scotland)
10. Owen Farrell (Saracens/England)
9. Mike Phillips (Bayonne/Wales)
1. Mako Vunipola (Saracens/England)
2. Richard Hibbard (Ospreys/Wales)
3. Adam Jones (Ospreys/Wales)
4. Richie Gray (Scotland)
5. Paul O'Connell (Munster/Ireland, captain)
6. Dan Lydiate (Dragons/Wales)
7. Justin Tipuric (Ospreys/Wales)
8. Toby Faletau (Dragons/Wales)
16. Tom Youngs (Leicester Tigers/England)
17. Cian Healy (Leinster/Ireland)
18. Matt Stevens (Saracens/England)
19. Alun Wyn Jones (Ospreys/wales)
20. Jamie Heaslip (Leinster/Ireland)
21. Conor Murray (Munster/Ireland)
22. Jonny Sexton (Leinster/Ireland)
23. George North (Scarlets/Wales)