Williamson, named player of the series after leading his side to an innings and 176 runs win and a 2-0 victory in the two-test series, has reached 919 rating points, bettering his own mark of 915 in December 2018.
ICC Cricket Hall of Famer Sir Richard Hadlee is the only other player from New Zealand to go past the 900-point mark, reaching a career-high 909 rating points in bowling in December 1985.
In the latest rankings update that includes the second test between South Africa and Sri Lanka in Johannesburg and the third test between Australia and India in Sydney, Steve Smith has leapfrogged Virat Kohli to second position after scores of 131 and 81 while Dean Elgar has moved to 13th position with knocks of 127 and 31 not out.
In other movements for New Zealand players, Henry Nicholls has gained three places to reach ninth among batsmen after his knock of 157 while fast bowler Kyle Jamieson's match haul of 11-117 has lifted him seven places to a career-best 21st place. With 36 test wickets so far, Jamieson is also fifth among all-rounders after only six tests.
Azhar Ali's knocks of 93 and 37 have helped him advance him seven places to 18th position and his compatriot Mohammad Rizwan's first-innings half-century has helped him gain 10 places to reach 37th position.
The drawn Sydney test saw Marnus Labuschagne consolidate the fourth position with a career-best 866 rating points after scores of 91 and 73 while fast bowler Josh Hazlewood has gained three places to reach fifth position with four wickets in the match.
For India, Cheteshwar Pujara's knocks of 50 and 77 have taken him from eighth to 10th position and Rishabh Pant's scores of 36 and 97 have helped him gain 19 places to reach 26th position. Hanuma Vihari and Ravichandran Ashwin have gained after their fighting knocks, as has Shubman Gill.
New Zealand rankings:
Batsmen
1 - Kane Williamson
9 - Henry Nicholls
12 - Tom Latham
16 - Ross Taylor
28 - BJ Watling
50 - Tom Blundell
Bowlers
3 - Neil Wagner
4 - Tim Southee
15 - Trent Boult
21 - Kyle Jamieson
