Ireland caused the first shock of the World Cup with a four-wicket triumph against West Indies in their opening Pool B match in New Zealand.
Lendl Simmons (102) shared 154 with Darren Sammy (89) as the Windies recovered from 87-5 to post 304-7.
But Ireland’s Will Porterfield and Paul Stirling put on 71 and Stirling (92) then shared 106 with Ed Joyce (84).
Niall O’Brien added 79 not out as Ireland won with 25 balls left, their fourth World Cup win over a Test team.
Having beaten Pakistan in their first World Cup in 2007 and England in the 2011 tournament, Ireland were almost considered favourites from the outset at the picturesque venue in Nelson on the south island.
The Windies, winners of the first two World Cups in the 1970s, now languish eighth in the ODI rankings, were skittled for 122 by England in a warm-up match and are rumoured to be in disharmony following the omission of Kieron Pollard and Dwayne Bravo from their squad.
Ireland, ranked 11th, reached the second group stage in 2007 and now have matches against the UAE, South Africa, Zimbabwe, India and Pakistan to try and secure a top-four spot in Pool B and a place in the quarter-finals.
Their intrepid fielding and accurate seam bowling after choosing to field quickly led to two wickets falling in the eighth over.
Big hitting Gayle and Marlon Samuels both launched towering straight sixes before both were dismissed by 22-year-old George Dockrell in the 22nd over, the left-arm spinner securing figures of 3-23 at one point.
Sammy unleashed some innovative strokes, often with ferocious power, in a thrilling partnership with Simmons, who accelerated stylishly as West Indies became the fifth successive team in the tournament to post in excess of 300 when batting first.
But far from overawed, the Irish openers punished some loose bowling in a fluent 13-over stand.
Man-of-the match Stirling hit three sixes in his pugnacious innings and was within eight of his sixth ODI hundred when, suffering from severe cramp, he edged behind in the 28th over with 128 still needed.
With the Windies looking ragged and forlorn, Joyce effortlessly guided the Irish within 32 of the target and despite three wickets in 17 balls, John Mooney, just as he did against England four years ago, struck the winning runs.
Ireland, coached by former West Indies batsman Phil Simmons, uncle of Lendl, next face fellow qualifiers UAE on 25 February.