Joe Schmidt is emerging as the Irish head coach since 2019, and current defense coach Andy Farrell is replacing.
Schmidt, 53, said he had decided on coaching and focusing on family commitments.
He has been with Ireland since 2013 and this year led them to his third Grand Slam and the first victory over his home country over New Zealand.
"I feel that Irish rugby is in good hands," Schmidt said.
"The management and the players have been amazing to work and the huge support we have had, especially at home in Aviva, but where we've always traveled, has been uplifting."
Farrell, 43, joined Ireland in April 2016 as a defense coach who had previously been a four-year spell as a British assistant coach.
The father of the current English international Owen Farrell, he was a double code player who won eight Cork caps when moving from a rugby league to a trade union.
Before serving as an assistant with England, Farrell opened the Aviva Premiership side of Saracens. He was also a defense coach for the 2013 British & Irish Lions World Cup qualifier in Australia.
Farrell has learned a lot from Schmidt
"It has a privilege to take into account such a prestigious role," he said.
"I've learned a lot Joea the last few years, and I'm learning him to continue over the next year, when the coaching team and players focus on to compete in two major tournaments in 2019."
Schmidt, who had escalated to the likely successor to New Zealand's Steve Hansen, supported Farrell's appointment as his successor.
"Coaches have been brilliant to work and Andy has made great impressions because he will be in the group," Kiwi said.
"His ability to lead and his understanding of the game will ensure that the team continues to move forward."
The heads of Schmidt win All Blacks
Schmidt, who led the Irish Six Nations titles in 2014 and 2015, has surpassed both Irish wins in New Zealand, including Dublin's 16-9 victory earlier this month.
He also led the team from eight to another in world rankings for five years at the helm.
Ireland reached the World Cup in 2015 during the quarter in Schmidt's possession, but hopes to get at least the first four for the first time in 2019.
Schmidt said last week that he was "overcoming a decision that has long since come".
"I know that I can not continue backwards and forwards. The family, which I have probably committed, there is this family, with whom I live Carton House [Ireland’s training base] as much as my family's home.
"So we have come together and tried to reconcile how we can best focus on both."
Schmidt's "Massive Impact" Irish Rugby – Connell
Prior to Monday's announcement, former Irish captain Paul O'connell said that the Irish Rugby Football Association should make "economically irresponsible" Schmidt leave his job.
"His coaching style and philosophy are filtered across the provinces," Connell told Matt Dawson at the Rugby Show at BBC Radio 5live.
"It's filtering down to schools and underage rugby, which greatly affects Irish rugby in general.
"So it's not just the results that he's delivering with the national team, which means that IRFU gets a lot of value when they pay for what they pay for him.