Colombo - Shane Watson grabbed three wickets as fired-up Australia restricted Ireland to 123-7 in a group B match of the World Twenty20 in Colombo on Wednesday.
Kevin O'Brien top-scored with 35, adding 52 for the fifth wicket with elder brother Niall (20) after Ireland had slipped to 33-4 by the eighth over.
Australia, who had briefly slipped below Ireland in the T20 rankings earlier this month, looked determined to teach the non-Test nation a cricketing lesson in the first ever T20 clash between the two sides.
The slump started with the first ball of the innings, which skipper William Porterfield hooked down fine-leg's throat to the great delight of bowler Watson.
In-form batsman Paul Stirling was caught at third man off Mitchell Starc and Ed Joyce holed out to mid-off against Glenn Maxwell after making 16.
Left-arm spinner Brag Hogg, the oldest player in the tournament at 41, struck with his second delivery when he trapped Gary Wilson leg-before for five.
The O'Brien brothers boosted the total with their partnership, before both fell in the space of four balls from Watson.
The West Indies are the third team in the group, from which two will qualify for the Super Eights round.
Ireland 123-7 in 20 overs (K. O'Brien 35, N. O'Brien 20, E. Joyce 16, S. Watson 3-26, M. Starc 2-20)