Welsh Rugby Union chairman Gareth Davies said the process of finding Gatland's successor dated as far back as Wales' tour of New Zealand in summer 2016.
Pivac meanwhile led the Scarlets to the Guinness PRO14 title in 2017 for the first time in over a decade, before again taking them to the final this season where they lost to Leinster, along with a European Champions Cup semi-final.
After more than 12 years at the helm, Gatland will bow out as the longest-serving and most successful head coach in the history of the game in Wales.
The Welsh Rugby Union has opted for Pivac over fellow Kiwis Dave Rennie and Scott Robinson, who were also on the shortlist for the post that will be vacated by Gatland upon completion of Japan 2019.
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A witness who assisted the actor at the scene, Jerry Zaslavsky, recalled that, "He seemed concerned for his friend and quiet". They all came together at the up-market Il Marino di Puntaldia restaurants after George had finished filming .
The 54-year-old's best showing at a World Cup was in an unlucky 9-8 loss to France in the 2011 semi-finals, having played most of the match with 14 players after captain Sam Warburton was sent off in the 19th minute. He was appointed Scarlets assistant coach in 2014 before taking over from Simon Easterby as head coach when the former Ireland global left to take up a role with the IRFU.
'I'll do everything in my power to live up to the expectations of the hugely passionate and knowledgeable rugby loving Welsh public'.
Davies said: "You only have to look at the way the Scarlets play and their recent achievements to get excited about the prospect of Wayne Pivac coaching Wales".
"We have avoided the feeding frenzy that can come at the end of a World Cup year and we have been meticulous in ensuring we have someone of the talent, experience, charisma and rugby acumen to do the very best possible job for Welsh rugby".