The project will mark Hugh Jackman's third and final Wolverine film. He has starred as the beloved adamantium clad character since 1999.
Stewart announced the "news" Saturday via Facebook and Twitter, saying: "Worst kept secret. #ProfessorX #Wolverine3"
Aside from this announcement, Stewart has spoken about the film previously, saying in an interview, "I understand that Professor Xavier will be making more than an appearance, however, and that intrigues me".
The much anticipated "Wolverine 3" is slated for a March 2017 release.