New Zealand's Rachin Ravindra and Kane Williamson showcased their prowess by remaining unbeaten against South Africa with centuries on the opening day of the first Test at Mount Maunganui on Sunday.

Despite featuring six debutants, the Proteas paid a hefty price for choosing to bowl first as New Zealand concluded the day at 258-2.

Williamson exhibited his resilient form, scoring 112 off 259 balls for his 30th Test century, while Ravindra notched up his maiden century, remaining unbeaten on 118 from 211 deliveries.

The duo formed an impressive partnership of 219, wearing down the South African attack that initially showed promise on the green-tinged Bay Oval pitch.

South Africa made an early impact as seamer Tshepo Moreki dismissed Devon Conway leg before wicket with his first ball, and Dane Paterson removed Tom Latham to leave New Zealand at 39-2.

However, Williamson and Ravindra weathered the storm, displaying patience and skill on a pitch that gradually eased out.

Ravindra, who had struggled in his initial Test innings, acknowledged the value of having Williamson as a guiding force. He said, "Kane was providing me with the perfect template for how to do it. Being able to learn from him throughout the partnership was great."

With only two loose shots during their stand, the pair will resume the next day, needing 38 more to set a record for the highest partnership for any New Zealand wicket against South Africa.

Williamson's century was marked by a dropped catch when he was 45, as Ruan de Swardt spilled a skied shot. Despite the chances, Williamson went on to secure his fifth century in the last six Tests, solidifying his position as the ICC's top-rated Test batsman.

Ravindra's left-handed brilliance came just a week after being named the ICC men's emerging cricketer of the year. Notably, the Proteas were without most of their first-choice players due to contractual obligations to the domestic Twenty20 league, resulting in the inclusion of six debutants in the squad.

Reflecting on their performance, South African pace bowler Olivier admitted that his team faded late in the day, emphasising the missed opportunities with dropped catches. He remained optimistic, stating, "It went their way, but there's still four days to go, so a lot can happen."