Kiwi great Kane Williamson has made the shock call to step down as New Zealand's Test captain less than a fortnight before the Blackcaps' red-ball tour of Pakistan.

Throughout his tenure in the top job, Williamson led the Kiwis from insignificance to the game's peak, winning 22 of his 40 Tests while holding the reins, as well as grinding out 8 draws and tasting defeat on just 10 occasions.

Williamson's crowning glory came during the inaugural World Test Championship Final in Southampton last year when the bearded maestro steered his side past Virat Kohli's Indian XI to claim the coveted mace.

Fittingly, the softly-spoken skipper earned red ink at the Ageas Bowl, partnering with his predecessor Ross Taylor to cap a golden afternoon for the former easybeats.

Citing a desire to place greater importance on his job with the bat, Williamson stepped down publicly on Thursday morning, with long-term lieutenant Tim Southee stepping up to become New Zealand's newest long-form captain.

Southee, 34, has been a mainstay since making his Test debut in 2008, collecting 347 wickets at an average of 28.99.

Speaking ahead of New Zealand's flight to the subcontinent, Williamson bowed out in a typically understated manner, professing that the time was right for change.

“Captaining the Black Caps in Test cricket has been an incredibly special honour,” Williamson reflected upon his resignation," Williamson announced.

“For me, Test cricket is the pinnacle of the game and I've enjoyed the challenges of leading the side in the format."

Though the Tauranga native will stay on as chief in both white-ball formats, the rigors of Test cricket had clearly worn the man so often praised for his patience at the crease.

“Captaincy comes with an increased workload on and off the field and at this stage of my career I feel the time is right for this decision," Williamson added.

“After discussions with NZC, we felt that continuing to captain the white-ball formats was preferable with two World Cups in the next two years."

Prior to the first Test in Karachi, Southee expressed his excitement at the elevation, no doubt stirred by the success that England's seamers have had of late in Pakistan.

AUCKLAND, NEW ZEALAND - JANUARY 30: Tim Southee of New Zealand celebrates as teammate Kane Williamson dismisses Josh Hazlewood of Australia on a run out to win the first One Day International game between New Zealand and Australia at Eden Park on January 30, 2017 in Auckland, New Zealand. (Photo by Anthony Au-Yeung/Getty Images)

“It's been a surreal few days and it's just a massive honour to be appointed as Test captain," the veteran bowler said.

“I love Test cricket, it's the ultimate challenge and I'm really excited by the opportunity to lead the team in this format.

“Kane's been an outstanding Test captain and I'm looking forward to working with Gary on how we can build on that.”

The leadership reshuffle also saw Tom Latham earn the title of Southee's deputy - a promotion that will likely be doubled in the summers to come.

During past instances of Williamson's absences, the opening batsman has played the role of stand-in skipper, leading the Blackcaps in nine Tests for four wins and six losses.

Williamson's choice to move aside comes at a precarious time for New Zealand cricket as a multitude of veterans, including Trent Boult, Martin Guptill and Colin de Grandhomme, have wound back their international dedication, preferring to open themselves up to the riches of franchise cricket.

Following the two-Test series in Pakistan, New Zealand will return home to host England and Sri Lanka in back-to-back series between February and March.