According to Deadline, Solo: A Star Wars Story will debut on May 15th at Cannes Film Festival.
The festival still is finalizing its competition film roster, but organizers won’t find a bigger film than this one. Sources said that the Lucasfilm origin story will premiere in a special screening May 15, before the picture makes its global premiere May 25.
George Lucas took Revenge of The Sith there in 2005 and Ron Howard has previously taken Willow, Far and Away, EDTV and The Da Vinci Code to Cannes Film Festival.
Until we here it officially from Lucasfilm, this will be treated as speculation for just now.