Rory McIlroy has won the US Open by eight shots, becoming the championship's youngest winner since 1923.

The 22-year-old from Holywood in Co Down led the field after every round.

He carded a two-under-par 69 for a 16-under-par total to triumph by eight strokes over Jason Day of Australia at the Congressional Country Club in Maryland.

'It's great to get this first major in the bag ... especially after what's happened the last couple of months,' said McIlroy, who banished memories of his Masters meltdown in April.

Going into the final round at Augusta National, he held a four-shot lead but tumbled out of contention with an ugly 80.

Triple major champion Padraig Harrington said McIlroy had set himself apart in potential.

'There might be people capable of winning a major, but there are not too many people capable of dominating and running away from the field in a major,' he said.

Last year’s US Open champion Graeme McDowell described his fellow Northern Irishman as the best player he had ever seen.

Taoiseach Enda Kenny described McIlroy's victory as both emphatic and inspiring, saying it ranks among one of the great achievements in any sport.

Minister for Transport, Tourism and Sport Leo Varadkar said McIlroy's performance confirmed the arrival of a new sporting hero.

Minister of State for Sport Michael Ring said it was very encouraging to see such a young sportsman doing so well, so early in his career.

McIlroy's final-round 69 gave him a 268 total that shattered the previous US Open record co-owned by Tiger Woods by four strokes.

Being 16-under for the championship was also four shots better than the old record set by Woods in 2000 at Pebble Beach.