A former police officer, Pivac began his coaching career with Auckland, winning the New Zealand Rugby coach of the year award in 2003. He went on to spend three years in charge of Fiji before spells with North Harbour and a second run with Auckland before heading to West Wales.
Pivac will become the fourth New Zealander to take charge of Wales, after Gatland and earlier Graham Henry (1998-2002) and Steve Hansen (2002-2004) who both went on to win the Rugby World Cup as head coach of the All Blacks.
Wales assistant coach Rob Howley, who has acted as caretaker coach at times in recent years, is expected to leave the set-up with Gatland in 2019.
"The union have been quite smart in trying to announce that early enough because there's no doubt that probably four or five coaches will be available post-World Cup and there will be a number of nations looking for new coaches as well," Gatland said regarding his successor last month during Wales' tour of Argentina.
"Wales have tried to get on the front foot and make that appointment early, but we just need to be smart in how we manage the next 12 months."