Ireland secured their place in the World Cup quarter-finals but were pushed all the way by Italy at the Olympic Stadium on Sunday.
Having won their first two games against Canada and Romania, Ireland knew a victory over the Azzurri would set them up for a pool decider against France in a week's time.
Ireland looked in control early on, with a Johnny Sexton penalty and a converted Keith Earls try giving them an early 10-3 lead.
But Italy fought back through their kicker Tommaso Allan, cutting the deficit to four points before Joshua Furno wasted a glorious chance to give the Italians the lead when he failed to carry the ball in his correct hand having been put clear on the left.
Still, Allan kept the Azzurri ticking over, and they trailed by just a point heading into the final half-hour following his third penalty.
Sexton settled Irish nerves with two more penalties around the hour and despite Peter O'Mahony's late yellow card, Ireland held on for the win.