Hayden scored 103 from 100 balls with 10 fours and two sixes. It was his 10th One-day International century and his fourth against New Zealand. Only compatriot Mark Waugh in 1996 and India’s Saurav Ganguly (in 2003) have scored three centuries in the same World Cup.
Captain Ricky Ponting scored 66 and Shane Watson, recalled to the side after missing the last three games through a calf strain, drove and swept powerfully to hit four fours and four sixes in his unbeaten 65 from 32 deliveries.
New Zealand took the field without fast bowler Shane Bond, who pulled out on Friday with a stomach complaint. They still took an early wicket when Adam Gilchrist threw his bat at the first ball of James Franklin's first over and was caught by Mark Gillespie on the third-man boundary.
Hayden and Ponting scored freely, although off-spinner Jeetan Patel, brought on in the fifth over, put a brake on the scoring with no boundaries after Hayden clumped Michael Mason for a six over long-on in the ninth over until Ponting pulled Scott Styris for four in the 15th.
Runs still came steadily with both batsmen bringing up their half-centuries and it came as a surprise when Ponting, who had stroked seven fours from 70 deliveries, was caught by Ross Taylor at mid-wicket off Patel.
Michael Clarke took two fours through the covers and one to third-man off Gillespie and Hayden drove Daniel Vettori past the bowler for three fours in a row then lofted Styris back over his head for his second six. He was out shortly after bringing up his century when Styris completed a fine caught-and-bowled turning around and running back to catch a skier.
Clarke hit Franklin for a brace of fours but was then clean-bowled one short of his half-century when he misjudged the left-armer's line.
Michael Hussey, promoted ahead of Andrew Symonds (11) stroked 37 and Watson took 24 off a Gillespie over including two sixes, on the way to his first World Cup half-century.
Scoreboard
AUSTRALIA:
A.C. Gilchrist c Gillespie b Franklin 1
M.L. Hayden c and b Styris 103
R.T. Ponting c Taylor b Patel 66
M.J. Clarke b Franklin 49
M.E.K. Hussey c Styris b Franklin 37
A. Symonds c Mason b Patel 11
S.R. Watson not out 65
G.B. Hogg not out 0
EXTRAS (LB-1, W-5, NB-10) 16
TOTAL (for six wkts, 50 overs) 348
FALL OF WKTS: 1-7 (Gilchrist, 1.1 ov), 2-144 (Ponting, 22.6 ov), 3-216 (Hayden (32.4 ov), 4-233 (Clarke, 35.3 ov), 5-257 (Symonds, 40.1 ov), 6-334 (Hussey, 49.3 ov).
DID NOT BAT: N.W. Bracken, S.W. Tait, G.D. McGrath.
BOWLING: Mason 3-0-27-0 (1nb); Franklin 8-0-74-3 (5nb); Patel 10-0-48-2 (1nb); Vettori 10-0-60-0 (2nb); Styris 10-0-50-1; Gillespie 6-0-67-0 (1nb), McMillan 3-0-21-0.
NEW ZEALAND: P.G. Fulton, S.P. Fleming, R.L. Taylor, S.B. Styris, C.D. McMillan, B.B. McCullum, D.L. Vettori, J.E.C. Franklin, M.R. Gillespie, J.S. Patel, M.J. Mason.
UMPIRES: Aleem Dar and Asad Rauf (both Pakistan).
TV UMPIRE: B.R. Doctrove (West Indies).
MATCH REFEREE: M.J. Procter (South Africa).—Reuters