Brian O'Driscoll rounded off a flowing backline move seven minutes after halftime for a converted try that put Ireland 19-6 ahead and Keith Earls touched down twice in the corner as Italy's hopes of a first quarterfinal evaporated.
Ronan O'Gara experienced none of the kicking problems that afflicted players in the other three pool matches under the roof of Dunedin's Otago Stadium, succeeding with six of his seven place kicks at goal and hitting the post with the other.
Otago Stadium was awash with green as the overwhelming majority of the 28,027 fans inside celebrated Ireland securing top spot in Pool C ahead of Tri-Nations champion Australia and a quarterfinal against northern hemisphere rival Wales in Wellington on Saturday.
"The games between us have been incredibly close over the last 7 or 8 years," captain O'Driscoll said. "Certainly in my career it's been to-ing and fro-ing and it's not mattered where the games have been. We've won in Cardiff and they've won in Dublin.
"I would envisage another close game." Italy coach Nick Mallett spoke before the game of how his side had more to offer than just forward power, but his players showed little else as they chased the big win they needed and their passion spilled over at times into foul play.
Leonardo Ghiraldini was fortunate referee Jonathan Kaplan missed an apparent eye gouge on prop Cian Healy and Mauro Bergamasco was involved in a handful of confrontations before swing a punch at Healy, forcing Kaplan to reverse a penalty that would have given Italy a shot at goal for 9-9 at halftime.
Instead, Ireland went into the interval 9-6 up, Kaplan took the captains aside in the tunnel to order an improvement in discipline, and O'Gara added another three points before the tries flowed.
O'Gara and Gordon D'Arcy made good ground following a lineout and Tommy Bowe raced through before slipping an inside pass to O'Driscoll, who touched down just to the left of the posts for his 45th international try.
Earls then collected a pass from Jamie Heaslip to turn and go over in the left corner, O'Gara drilling the conversion from just inside the touchline to put Ireland three scores clear at 26-6 with more than 25 minutes remaining.
Bowe looked to have scored a late breakaway try after hacking the ball downfield past the tiring Italian defense but he got neither the score nor a penalty try despite having been hauled back while attempting to touch down.
It didn't matter. Andrew Trimble broke from the quarterline restart and drew his man in before popping a gentle pass into the arms of the onrushing Earls, who raced in again.
With O'Gara having been withdrawn to an ovation for his 16-point haul; Jonathan Sexton added a sideline conversion to his earlier penalty to complete the scoring with the last kick of the match.
Mirco Bergamasco never got a chance to add to his two first-half penalties and, with his brother replaced shortly into the second half and Martin Castrogiovanni off with what looked to be a right hamstring injury, Italy could not sustain its efforts up front.
Italy's most experienced starting lineup ever with a total 744 caps competed well in the scrum and mauled strongly in the first half but had little to offer in the loose, with players failing to spot overlaps and gaps when they did occur.
Mallett won't get the chance to put those failings right. The former South Africa coach has led Italy for the last time, with Jacques Brunel set to take over before the start of the Six Nations in February.
Ireland lost hooker Rory Best to injury but was able to take off lock Paul O'Connell for the final quarter to preserve him for the quarterfinals. O'Gara also trotted off to be replaced by Sexton for the last 14 minutes, with only the penalty onto the post and a first-half drop goal attempt that faded past the left post marring his kicking performance.
With Kidney looking ahead, Healy, Conor Murray, Stephen Ferris and O'Driscoll also went off late on. Man-of-the-match Sean O'Brien stayed on until the end.
In Wellington, New Zealand winger Zac Guildford scored four tries as the All Blacks temporarily lifted the dark pall over their rugby World Cup campaign with a 79-15 victory over Canada in their final Pool A clash on Sunday.
With the All Blacks coming to terms with news that flyhalf Daniel Carter had been ruled out of the tournament after tearing a groin tendon in training, Guildford popped up all over the field and had a hand in three other tries against the Canadians.
"I think... he played particularly well, which was very pleasing," Henry told reporters.
"He has put his hand up and is a selection candidate for next week. I'm very pleased for him," he added of the All Blacks' quarterfinal against Argentina next Sunday.
Carter's exit from the tournament was described earlier by coach Henry as a "major" blow to the All Blacks, though the team also suffered a series of other injuries in the match.
Carter's replacement Colin Slade limped off in the second half, as did utility back Israel Dagg, while loosehead prop Tony Woodcock was forced off following a head clash with Canada's Adam Kleeberger.
"His health is okay. He told me he is fine," Henry told reporters of Woodcock, who appeared to be knocked cold in the collision. "He got a pretty severe head knock but he recovered pretty quickly. I think he'll be fine." Henry added that Slade had been taken off as a precaution because "he hasn't played much footy recently.”
Guildford, making his first start of the tournament, ran in a hat-trick of tries in the first half as the All Blacks backline cut the Canadians to shreds with their pace, width and ability to push their hands free of the tackle.
Guildford also helped set up tries for Dagg and veteran fullback Mils Muliaina, while Victor Vito smashed over after the All Blacks had demolished the Canadian scrum inside their own 22-meter area.
Slade had difficulty kicking in the swirling northerly breeze, adding just two conversions and a penalty in the first half.
Canada had defended for most of the first half but managed to score just before the break when winger Conor Trainor crossed in the corner following a sustained buildup.
Trainor added his second try immediately after halftime when he fell on the loose ball from a kick ahead and slid over. Ander Monro converted to make it 37-15.
The All Blacks lost some structure in the second half but still managed to post their highest score against Canada as Jimmy Cowan, Jerome Kaino (two), Sonny Bill Williams, Guildford and Vito all crossed.
Piri Weepu slotted four conversions as the All Blacks surpassed their previous highest score against Canada of 73-7, which they posted in 1995.
In Hamilton, dark horses Wales charged into the World Cup quarterfinals Sunday with a classy 66-0 win over Fiji to set up a quarterfinal showdown with Ireland, which suggested they may be hitting form at the perfect time.
In wet and blustery conditions at Waikato Stadium, Wales buried 2007's shock loss to the Pacific islanders with a nine-try romp to set up a last-eight clash against Ireland, Italy or Australia.
Warren Gatland's men finish second in Pool D with 15 points from three wins and a narrow, one-point loss to defending champions South Africa, with confidence high and comparatively few injuries heading into next week's quarterfinals.
And Rhys Priestland and veteran Stephen Jones delivered a perfect kicking performance of all nine conversions and a penalty as Wales made a mockery of the woes, which have affected other teams.
Fiji made wholesale changes after their defeat to Samoa and it showed as slick Wales totted up four five-pointers before the break for the lone bonus point they needed to progress, while amassing a 31-0 half-time lead.
In afternoon drizzle at Waikato Stadium, Wales went ahead after six minutes when 22-year-old captain Sam Warburton gobbled up an overthrown Fiji line out and Jamie Roberts jinked through Fiji's midfield to score under the posts.
Apart from occasional forays down the left, Fiji were unthreatening and Wales opened them up with a swift interchange between Roberts and George North on their left to release Scott Williams, who swerved past the last defender to score.
Wales were rampant and another swift move down the right involving Roberts, prop Huw Bennett and Tongan-born No. 8 Toby Faletau — and a strong hint of forward pass — put 19-year-old North through for their third.
And they sealed the bonus point just before half-time when the impressive North received quick line-out ball and dummied his way through to set up Warburton for a diagonal run to the line.
More pinball passing put Roberts in for his second when North did a swift one-two with Priestland to set up the center for an easy score.
Replacement hooker Lloyd Burns bagged his first international try and right wing Leigh Halfpenny was the grateful recipient when Fiji's Albert Vulivuli made a hash of gathering a kick behind the defense and gave him a free run to the line.
Substitute scrumhalf Lloyd Williams caught Fiji's defensive napping when he darted over for a poacher's try and center Jonathan Davies grabbed the ninth and final score in the dying seconds.
In Palmerston North, New Zealand, Argentina secured their place in the quarterfinals of the rugby World Cup with a 25-7 win over Georgia on Sunday.
Coming into the game in Palmerston North needing only a bonus point to progress to the knockout stages, Argentina's victory cemented second spot in Pool B behind England and set up a clash with New Zealand in the last eight.
However, Argentina struggled for long periods before finally putting their lower-ranked opponents away in a match littered with handling errors.
Two late tries put some gloss on the scoreline for Argentina but Georgia fought hard for 80 minutes in their final match of the tournament, with a strong physical performance let down by poor handling and a high penalty count.
After a scoreless first 30 minutes Argentina winger Juan Jose Imhoff crossed the line after the South Americans recycled the ball quickly through a number of phases and stretched the Georgian defense to breaking point on their right flank.
But Georgia struck back within five minutes to take a surprise 7-5 lead into half time. A slick break down the left wing from within their own half by Lekso Gugava was followed by a chip kick, and flyhalf Lasha Khmaladze won the race to the ball to score the try.
Argentina were let down by some poor kicking in the first half with captain Felipe Contepomi failing to convert Imhoff's try and missing a pair of penalties.
However, they regained the lead early in the second half after spending most of the first 10 minutes pounding the Georgian line, eventually earning a penalty close to the posts, before adding another penalty 10 minutes later.
Contepomi stretched the lead further in the 68th minute as slick passing saw the Argentinians break down the right and quick ball gave them a massive overlap for Contepomi to score on the left.
Argentina added another try to replacement Agustin Gosio just before the final whistle.
Argentina will now face favorites New Zealand in the quarterfinals on Oct. 9, with the hosts still reeling from news that flyhalf Daniel Carter has been ruled out of the remainder of the World Cup with a groin injury.
