Gatland steps down after the 2019 World Cup and fellow New Zealander Pivac has always been touted as his successor.
The reflex reaction whenever a significant coaching vacancy crops up is often to look to New Zealand for candidates.
"Both Wayne and Warren and their coaching teams, our global players, supporters and everyone at the Scarlets now have clarity and there is no underestimating the positive benefit to be gained from having the time to plan properly for the future".
Wayne Pivac, head coach of Welsh rugby union side Scarlets, will take over from Wales coach Warren Gatland after he steps down following the 2019 World Cup in Japan, Wales Rugby Union said on Monday.More news: Iran warns India of curtailing special privileges if oil imports reduced
Pivac has enjoyed notable success with the Scarlets, winning the Pro12 in 2017 before reaching the final - and the last four of the European Champions Cup - in 2018.
Over a dozen years, Gatland won the Six Nations Championship in 2008 and 2012 and managed 52 victories in 105 matches with the Wales rugby team. By that time, he will have been in charge for 12 years.
He said the decision to take the Wales job was "a no-brainer".
'I'll do everything in my power to live up to the expectations of the hugely passionate and knowledgeable rugby loving Welsh public'.More news: Ivan Perisic hails 'dream' goal as Croatia reach final
"I felt more comfortable putting my name forward and I feel as if I am a Welsh coach".
WRU chairman Gareth Davies and chief executive Martyn Phillips host a scheduled press conference later.
"Wayne will bring the holistic approach to the job we are looking for and will be immediately ready to pick up where Warren leaves off - he offers the complete package and we are delighted to have secured his services".More news: Thai Cave Rescue Is Becoming a Movie