The Black Caps thrashed a makeshift Irish side by 290 runs in what was the biggest margin of victory in the history of one-day international cricket, surpassing India's 257-run defeat of Bermuda at last year's World Cup.
New Zealand's total of 402 for two was also their highest one-day international total and an opening stand of 274 runs between Brendon McCullum and James Marshall was the fifth highest for any wicket.
In reply, Ireland were scuttled out for 112. McCullum claimed his first ODI century with a knock of 166 from 141 deliveries that featured 11 boundaries and ten sixes.
Southee and Michael Mason claimed three wickets apiece while only some lusty hitting from tail-ender Peter Connell, who top-scored with 22 not out, ensured Ireland hoisted their tally above the 100 mark.
