New Zealand have posted 291 runs in their Group A match against Australia at the Champions Trophy cricket tournament..
Williamson made 100 runs of 97-balls with eight boundaries and three sixes. Ronchi made a quick fire 65 off 43 deliveries which included nine boundaries and three sixes.
For Australia, fast bowler Josh Hazlewood produced an excellent display of pace bowling to return figures of 6/52, three of those wickets coming off four deliveries in the penultimate over of the innings.
Fellow pacer John Hastings had figures of 2/69 while fast bowler Pat Cummins got one wicket.
Electing to bat first on winning the toss, New Zealand were off to a steady start as openers Ronchi and Martin Guptill took the total to 40 runs in the sixth over.
Hazlewood struck the first blow for Australia when Guptill was outfoxed by a bit of extra bounce and was caught by Glenn Maxwell at point.
A heavy drizzle led to suspension of play for around one and a half hours forcing the officials to reduce the match to 46 overs a side.
Williamson and Ronchi however, did not let the break affect their focus, adding 77 runs between them off 60 balls.
Hastings brought the partnership to an end when he sent Ronchi back to the pavilion, courtesy another excellent catch at point by Maxwell.
Williamson and Taylor then put together 99 runs in 18.1 overs to put the Kiwis on course for a big total.
Taylor was dismissed when he mistimed a slower ball from Hastings, offering a simple top edge to Moises Henriques in the covers.
Williamson completed his century exactly five overs later, smashing Hastings for a boundary before taking a quick single to reach triple figures, his ninth in One-Day Internationals and his first against Australia.
The right-hander was dismissed off the very next ball he faced when he was run out thanks to an accurate throw by Cummins.
Williamson’s departure heralded a mini collapse by the Kiwis as they lost the remaining six wickets over the next six overs.
Hazlewood clinched the wickets of Adam Milne, Mitchell Santner and Trent Boult in the 45th over to bring the curtains down on the New Zealand innings.