Bridgetown - 's highest Test score put New Zealand in control at 331 for seven in their second innings, a lead of 307 runs, on a rain-shortened fourth day of the third and final Test at Kensington Oval on Sunday.
His unbeaten 161 in over six hours at the crease was the highlight of a determined Black Caps effort that tilted the balance of an intriguing match.
When heavy rain swept across the ground in mid-afternoon, the tourists were poised to build on what was already a challenging target at 314 for six, ahead by 290.
Only 20 more minutes of play was possible on the resumption, with one more wicket being lost for the addition of another 17 runs, before more rain rolled in.
That left New Zealand captain Brendon McCullum to contemplate his options for a declaration going into Monday's final day, weather permitting.
A key factor in his consideration will be that the highest winning fourth innings total in a Test match at the venue is 311 by the Brian Lara-led West Indies against Australia in 1999.
Williamson's innings was a masterful effort of concentration and shot-making.
The elegant right-hander stroked 22 boundaries in a classy innings, putting the seal on an outstanding series for the 23-year-old that has brought him 413 runs so far.
McCullum contributed to his team's improved second innings effort, scoring 25 in a 67-run fourth-wicket partnership with Williamson before he fell lbw to Kemar Roach in the fourth over of the day.
Allrounder Jimmy Neesham picked up from where his captain left off and was even more impressive, striking four sixes and three fours in an entertaining 51 out of a fifth-wicket stand of 91 before another powerful drive by the left-hander off debutant Jason Holder found Kraigg Brathwaite at short extra-cover.
Wicketkeeper-batsman B.J. Watling nudged and deflected his way to 29 while Williamson took centre stage in a sixth-wicket partnership of 79 as an increasingly frustrated Denesh Ramdin and his West Indies team seemed to run out of ideas.
Roach and the second new ball eventually brought the breakthrough after lunch, Watling cutting the fast bowler to Holder at backward point to become the Barbadian's 100th Test wicket in his 26th Test, the 19th West Indian in the history of the game to reach that landmark.
It was also his fourth wicket of the innings and eighth of the match, although his personal success was only a momentary distraction from the greater challenge facing the West Indies.