The Black Caps' skipper kept his cool at the end of a nerve-jangling match that went down to the last over with eight runs still required, hoisting Andile Phehlukwayo for a huge six over midwicket to bring up a majestic century.
But along with the plaudits, he also earned some brickbats along the way as the innings was shrouded in controversy.
In the 38th over of the chase when the match was still in the balance, Williamson got a reprieve that proved gut-wrenching for the South Africans. The moment proved pivotal as Williamson was the anchor around which the Kiwis completed the chase, virtually knocking South Africa out of the tournament.
The right-hander had tried to play a fizzing leg-break by Imran Tahir fine towards the third man boundary but failed. Tahir was convinced he had edged the ball but Quinton de Kock, behind the stumps, and the umpire Nigel Llong were oblivious to any contact.
Had the captain, Faf du Plessis, reviewed, Williamson would have departed for 76 with replays and ultra-edge showing that there was the faintest of edges.
Now, some fans have started questioning why the New Zealand captain did not walk after being caught behind. While some defended the decision and said it was wise to wait for the umpire decision, others said it was not in the spirit of the game.
No! #Proteas just can't get a break. Tahir finds the edge of Williamson's bat but only he appeals. It's official, the cricket gods hate #SouthAfrica.— I am an African (@Clint_ZA) June 19, 2019
Oh, and from his reaction Kane knew he hit it. Pity honesty has no place in professional sport. #NZvSA #CWC19
Shame on Kane Williamson... Could have walked when edged #NZvSA— Nasir (@sh_nasir) June 19, 2019
#NZvSA #CNN @CNN #FoxNews #outnumbered #SouthAfrica @cricketworldcup #WorldCup— Stanist (@stanistism) June 19, 2019
South Africa is again choking!!
Kane Williamson should have walked off. As he holds honesty and sportsman spirit at highest standard!!
Honestly his smile clearly indicated he nicked it!
Some even drew comparisons to Indian skipper Virat Kohli, who had decided to walk in the game against Pakistan after he felt he nicked the ball, although it was later revealed he had not edged it.
Can't believe Williamson didn't walk. Humare hi launde jyada shareef hai #NZvSA— LacaJet (@ThatGuyJSR) June 19, 2019
There are two kinds of people in the world - One is Virat Kohli type and the other one is Kane Williamson type. Completely opposite but equally amazing. #NZvSA— Rohit Lawand (@LawandRohit1) June 19, 2019
There were others who said it was smart of Williamson to not walk when the umpire did not give him out and South Africa did not even review the decision.
Unlike stupidity of Virat Kohli who walked out without even an edge, Kane Williamson stands firmly as Umpire and Keeper not interested, review lost and as a result South Africa out of World Cup 2019 and New Zealand entering Semis #NZvSA #CWC19 https://t.co/NGZOjRMdmY— Sharan (@SharanRoars) June 19, 2019
Then there were others who did not want to miss the opportunity to troll South Africa and Quinton de Kock for the DRS blunder.