Kristian Woolf will replace the departing Justin Holbrook as St Helens head coach, the Super League club have announced.
Woolf has signed a two-year deal, with Saints also holding an option for a third season, and begins his new job at the start of November.
The 44-year-old will arrive from Newcastle Knights, where he served as an assistant to Nathan Brown before taking charge on an interim basis following the departure of the former Saints boss.
He was recently sacked as Tonga coach following a five-year stint at the helm that included steering them to the semi-finals of the 2017 Rugby League World Cup.
"I'm excited and privileged to be joining St Helens as head coach," Woolf - who has also previously worked for Brisbane Broncos - said in a statement released by Saints.
"It's something I have always wanted to do and it's a great opportunity for me.
"St Helens is a club with an amazing history and I'm confident we can achieve great things together."
St Helens chairman Eamonn McManus is "very confident" Woolf can build on the strong work done by Holbrook, who confirmed in July he will take over at Gold Coast Titans in 2020.
However, before he exits, the NRL-bound coach will hope to sign off by leading his current employers - who have clinched the League Leaders' Shield this year but lost to Warrington Wolves in the Challenge Cup final - to glory in Super League.
"We consider that Kristian is ideally qualified and placed to build upon the current success of the team and the club," McManus said of Woolf.
"He has the experience and expertise to bring the best out of our existing squad and to improve it further.
"We are very confident that the Saints will seriously compete for honours under his tenure and that we will continue to play attractive and exciting rugby league."