Ireland will face Wales in the World Cup quarter-finals on Saturday after trouncing Italy to top Pool C.
Three Ronan O'Gara penalties helped the Irish to a 9-6 half-time lead and their complete second-half dominance was rewarded with three well-worked tries.
Brian O'Driscoll touched down for the first and then birthday boy Keith Earls scored two tries.
O'Gara kicked a further penalty and two conversions, while Jonathan Sexton landed one penalty and a conversion.
Mirco Bergamasco kicked Italy's only points with two first-half penalties.
O'Gara eased early Irish nerves with a seventh-minute penalty but Bergamasco levelled the scores by slotting over his first kick at the posts three minutes later.
As both packs battled for supremacy, Ireland were awarded another penalty when Mauro Bergamasco was penalised at the breakdown, but O'Gara's effort cannonned off the upright.
The Irish fly-half was successful with his next attempt in the 16th minute however after Italy offended at a line-out.
Ireland's advantage lasted only three minutes as they were penalised for collapsing at the ruck and Bergamasco knocked over his second penalty to restore parity.
There was controversy soon after when hooker Leonardo Ghiraldini appeared to make contact with the eyes of Irish hooker Cian Healy but referee Jonathan Kaplan did not see the incident.
Kaplan was the centre of attention on the half-hour when he disallowed a Tommy Bowe try for a forward pass by Sean O'Brien, a decision which looked dubious when viewed on replays.
O'Gara nudged his side ahead again with his third penalty after Italy were pulled up for being offside at a ruck.
Italy squandered an opportunity to draw level just before the interval after Paul O'Connell was penalised for not rolling away.
Bergamasco hit the upright with the resulting penalty.
Ireland started the second half in impressive fashion and O'Gara knocked over his fourth penalty in the 43rd minute.
An audacious drop-goal attempt by O'Gara then went wide of the posts as Ireland tried to make their territorial dominance count.
O'Driscoll scored the first try of the game in the 47th minute when he ran in under the posts after anticipating and accepting a deft inside pass from Bowe, who had broken through the Italian defence.
O'Gara converted to increase his side's lead to 13 points.
Winger Earls touched down for Ireland's second try five minutes later.
Gordon D'Arcy fended off a series of attempted Italian tackles and passed to charging flanker Stephen Ferris, who offloaded for Earls to score in the corner.
O'Gara continued his excellent kicking form by adding the conversion.
Rob Kearney almost grabbed the third try when he made a dive for the corner but the television match official ruled that he had been held up short of the line.
Ireland lost Rory Best with a collarbone injury and O'Connell with a hamstring problem, but continued to outplay their opponents.
Sexton knocked his penalty between the posts soon after replacing O'Gara.
Bowe just failed to touch down for a try but Earls celebrated his 24th birthday in style by scoring his second in the final minute after a break from replacement Andrew Trimble.
Sexton added a difficult conversion from near the touchline to complete a special night for the Irish.
Ireland: Kearney, Bowe, O'Driscoll, D'Arcy, Earls, O'Gara, Murray; Healy, Best, Ross, O'Callaghan, O'Connell, Ferris, O'Brien, Heaslip. Replacements: Cronin for Best (53), Ryan for O'Connell (58), Sexton for O'Gara (67), , Court for Healy (72), Leamy for Ferris (72), Reddan for Murray (73), Trimble.
Italy: Masi, Benvenuti, Canale, Garcia, Mirco Bergamasco, Orquera, Semenzato; Perugini, Ghiraldini, Castrogiovanni, Geldenhuys, Van Zyl, Zanni, Mauro Bergamasco, Parisse. Replacements: Lo Cicero for Castrogiovanni (34), Bocchino for Orquera (40), Derbyshire for Mauro Bergamasco (49), Gori for Semenzato (56), Bortolami for van Zyl (61), Ongaro for Ghiraldini (67).
Referee: Jonathan Kaplan (South Africa)