Retiring George North returns to Wales side against Italy in Six Nations
Gatland left out North and midfield partner Nick Tompkins for the 45-24 home defeat to France this past weekend, as Wales now face a fifth defeat in a row in this year's competition.
"I've decided the game on Saturday will bring my international career to an end. After 14 years it feels like now is right time to step away," North said in a statement.
"I have loved and cherished every second in a Welsh shirt and been able to play alongside some fantastic teammates."
North is third on the all-time list of Wales' most capped players with 120 appearances, behind Alun Wyn Jones (158) and Gethin Jenkins (129). He also played three times for the British & Irish Lions.
"George has contributed hugely to Welsh rugby, in an incredible career starting as an 18-year-old," Gatland said.
"The way that he burst onto the scene. I can remember seeing him play and thinking we need to cap this kid. He’s been incredible as a rugby player, but I think the most important thing is how he’s contributed to the squad as a person over the years."
Wales captain Jenkins Dafydd Jenkins is back in the second row to partner Adam Beard against Italy, while North and Tompkins come in for Joe Roberts and Owen Watkin respectively.
The other changes to the starting line-up see flanker Alex Mann replace lock Will Rowlands to allow Jenkins to make his switch, while prop Dillon Lewis comes in for Keiron Assiratti in the front row.
Hooker Elliot Dee also retains his place having been a late replacement for the injured Ryan Elias against France.
Wales may be rebuilding their squad with an eye on the 2027 World Cup in Australia, but five defeats in this year's Six Nations would be a major embarrassment and a place a spotlight on the work being done by Gatland.
They come up against an Italy side buoyed by a 31-29 victory over Scotland at the weekend, and who also held France 13-13, with their improvement under new coach Gonzalo Quesada apparent, in contrast to the form of Wales.
"This is an important game for us. We definitely don't want to finish bottom and the squad is hungry to win," Gatland said.
"We're still looking for that 80 minute performance and have spoken about needing to be better in the big moments especially."
The last time Wales lost all five games in the Six Nations was in 2003. They will avoid the wooden spoon with a win by more than seven points on Saturday as long as Italy do not get a try-scoring bonus-point.