Williamson returns to the Black Caps after a hamstring strain sidelined him during the recent home T20I series win over Pakistan.
Meanwhile, fresh from being named emerging player of the year by the International Cricket Council, rising star Ravindra will take the place of veteran Henry Nicholls in the middle order. The young all-rounder played the last of his three Tests in January 2022.
“Rachin Ravindra is another player who has really impressed us with his contributions to the team over the past 12 months in international cricket. We've been particularly pleased with his ability to adapt and learn in different roles,” said head coach Gary Stead.
“It was a very tough decision. Henry has been part of the squad for 56 Tests. Whenever you leave a player out, it weighs heavy, but we felt it's time for Rachin.”
Uncapped seamer Will O'Rourke will be added to the squad for the second Test in Hamilton, starting February 13, when he could make his debut.
The first game begins February 4 at Mount Maunganui with hosts New Zealand chasing a first-ever Test series win over the Proteas.
South Africa have named an inexperienced squad, with the bulk of their first-choice players committed to the SA20. Eight of the 15-man Proteas squad have yet to play Test cricket, including captain Neil Brand.
“It's an honour to be involved in any Test match and I know the players are looking forward to the start of a big Test summer - in what is a big year of Test cricket home and away. The Proteas are a highly competitive team across formats and, having never won a Test series against them home or away, we expect two stern challenges," said Stead.
Squad - Tim Southee (c), Tom Blundell, Devon Conway, Matt Henry, Kyle Jamieson, Tom Latham, Daryl Mitchell, Will O'Rourke* (for second Test only), Glenn Phillips, Rachin Ravindra, Mitchell Santner, Neil Wagner, Kane Williamson, Will Young.