Ireland, who finished top of their pool with this victory, will now face Wales in the first quarter-final at Wellington Regional Stadium next Saturday.
Captain Brian O’Driscoll crossed the Italy line first in the 47th minute and was soon followed by wing Keith Earls as Ireland overran their opponents.
With just over a minute remaining, wing Tommy Bowe came close to scoring, but failed to ground the ball in a chase with two Italian defenders.
However, Earls scored his second and Ireland’s third try when sprinting into the left corner. Replacement Jonathan Sexton kicked the conversion for 36-6.
The Irish had held a 9-6 lead following a scrappy first half after Ronan O’Gara hit three penalties to Italian Mirco Bergamasco’s two.
Succession of penalties
The succession of penalties continued just two minutes into the second half as O’Gara made it 12-6 when Italy were penalised for not rolling away at a ruck.
O’Gara failed to extend Ireland’s six-point lead a few minutes later when he missed a drop goal attempt from just outside the Italian 22m.
However, Bowe broke through a gap in the Italy defence on the 47th minute, offloaded to centre O’Driscoll and he sprinted over the line for the match’s opening try. O’Gara kicked the conversion for a 19-6 lead.
Then it was happy 24th birthday for left wing Earls when he crossed in the corner five minutes later after Gordon D’Arcy sparked the attack. O’Gara added the extras for a 26-6 advantage.
Ireland were well on top now and came close to adding a third try through Rob Kearney, but the full back was held up by the Azzurri defence.
Sexton, who had come on for O’Gara in the 67th minute, then landed a penalty three minutes later to extend Ireland’s lead to 29-6 after Italy did not release the ball in a ruck.
Nerves appeared to get the better of both sides in this crucial match as there was little flow to first-half play, but several handling errors and numerous penalties.
The closest to a try in the first half came when Ireland’s Bowe crossed the Italian line, only for play to be taken back by the referee for a forward pass from man of the match Sean O’Brien.
Ireland qualify for the quarter-finals of RWC 2011 and will play Wales on Saturday, 8 October in Wellington.
– The final of RWC 2011 is now guaranteed to feature one team from the northern hemisphere and one from the southern. This will be the sixth of the seven RWCs in which this has happened.
– Brian O’Driscoll joins Brian Lima (SAM) and Gareth Thomas (WAL) as the only players to score tries at four different RWCs.
– Keith Earls is the fifth person to score at least one try on his birthday at the RWC.
– Earls and Chris Latham (AUS) are the only players to have scored more than one try on their birthdays at RWCs. Latham scored two against Japan at RWC 2007.
– Ronan O’Gara has scored with 16 of his 19 place kicks at RWC 2011. Only Stephen Jones (WAL) and Morgan Parra (FRA) have a better scoring rate among place kickers with at least 10 attempts.
– Ireland scored five penalties in this match. Only Georgia have scored more penalties (six) in a RWC 2011 match.
– Ireland became the seventh team to score 100 or more points at RWC 2011. All seven have made it to the quarter-finals of the competition, with only Argentina making the last eight having scored fewer than 100 points.
– Ireland have now scored 809 points at RWCs. They are the eighth team to go past 800.
– The RWC 2011 tournament points total has now gone past the 2000 mark and stands at 2022.