Leslie Benzies, head of Scotland-based Rockstar North, has departed the studio.
Benzies helped shape the Grand Theft Auto series and had worked at Rockstar Games since 1999, when it was called DMA Design.
In a statement to Kotaku, Rockstar commented, "We can confirm that Leslie Benzies went on sabbatical on September 1, 2014 and has decided not to return to work for the company. We are very grateful for Leslie's contributions to Rockstar over the last 15 years as we worked together to make some amazing games.
"Leslie helped us build an incredible team that will continue to create great experiences for our fans. Leslie will always be a friend to the company and of course we are going to miss him but we wish him the absolute best for the future."
Benzies oversaw development of all major GTA games and was one of Rockstar's most important staffers, along with co-founders Sam and Dan Houser.
Rob Nelson, an animation director on GTA5's PC, PS4, and Xbox One port, and art director Aaron Garbut are the current co-heads of Rockstar North. Nelson recently moved to Edinburgh from Rockstar's New York headquarters while Garbut has been at Rockstar North for many years.