O'Connell's inclusion means the in-form Mick O'Driscoll moves to the replacements bench as head coach Tony McGahan makes just three changes to the side that played the Ospreys home and away in the most recent rounds.
Peter Stringer retains the number 9 jersey for what will be his 89th Heineken Cup appearance, with Tomas O'Leary providing back-up on the bench.
Meanwhile, the Heineken Cup's most-capped player, John Hayes, gets the nod to start at tighthead prop ahead of Tony Buckley. It will be Hayes' 98th match in European club rugby's premier tournament.
London Irish also host the Ospreys in Pool 3 on Sunday afternoon, and mathematically, all four teams are still in with a shout of qualifying for the quarter-finals.
Toulon are in pole position on 13 points, with Munster (11), the Ospreys (10) and London Irish (5) trailing them. Munster are at home to Irish in round 6, at the same time as Toulon pay the Ospreys a visit.
Wisely not daring to look beyond this Sunday's action, Munster lock Donncha O'Callaghan explained how the two-time champions are approaching their trip to the south of France.
"As far as we're concerned, it's a case of winning on Sunday, simple as that." said O'Callaghan, the man-of-the-match in last weekend's Magners League win over Glasgow Warriors.
"This is what we're all about. It's really what we were reared on in terms of the professional club game. The Heineken Cup is where it's at."
"It was the first international club competition. It's different to the league obviously because it's knockout rugby. You could lose three four games in the Magners League and still qualify for the knockout stages. You don't have that leeway in this competition."
He added: "We've been here before. In this situation. There was Gloucester at Thomond Park. There was the quarter-final away to Stade Francais with a gale-force wind in our faces.
"There was Perpignan away. People might write us off. We'll never do that to ourselves."
MUNSTER (v Toulon): Paul Warwick; Doug Howlett, Keith Earls, Sam Tuitupou, Johne Murphy; Ronan O'Gara, Peter Stringer; Wian du Preez, Damien Varley, John Hayes, Donncha O'Callaghan, Paul O'Connell, James Coughlan, David Wallace, Denis Leamy (capt).
Replacements: Mike Sherry, Darragh Hurley, Tony Buckley, Mick O'Driscoll, Donnacha Ryan, Niall Ronan, Tomas O'Leary, Lifeimi Mafi.