Victory at the Rose Bowl saw World Cup finalists New Zealand go 2-1 up in the five-match series.
The Black Caps, chasing 303 for victory, were wobbling at 36 for two.
But a New Zealand record third-wicket stand of 206 between Williamson (118) and Ross Taylor (110), ultimately proved decisive.
There have long been anguished debates about whether advances in bat technology and modern-day power-hitting are making ODI cricket too much of a batsmen's game.
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Indeed his final scoring shot, in a sublime 113-ball innings which included 12 fours, was a seemingly effortless straight six off David Willey.
"I don't think aggressive has to mean slogging or hitting the ball 150 metres," said man-of-the-match Williamson, who also bowled England captain Eoin Morgan for 71 with his off-spin.
"I think the style of play is what you want to achieve in an innings and the runs you want to get and that dictates who's picked," added Williamson following his seventh hundred in 77 matches at this level.
New Zealand suffered a setback before this match when in-form paceman Trent Boult was ruled out of the rest of the tour with a back injury.