The trio will begin their opening round at 1459 local time (1359 GMT) on Thursday as world number two McIlroy looks to claim his fifth major title at the course where he won the Open in 2014.
Rahm, the world number three, is aiming to become the first Spaniard to lift the Claret Jug since Seve Ballesteros in 1988.
Australian Cameron Smith (29) begins his title defence at 0958 in the company of U.S. Open champion Wyndham Clark (29) and Olympic gold medallist Xander Schauffele (29).
American world number one Scottie Scheffler (27) is also among the early starters in a group with England's Tommy Fleetwood (32) and Australian Adam Scott (43).
Royal Liverpool member Matthew Jordan (27), who came through qualifying to earn a place in the 156-man field, will hit the opening tee shot of the 151st British Open at 0635.
