Barack Obama's 60th birthday may have gotten scaled back from a bash to a small shindig ... but it's still about as star-studded as it gets.
Several celebs still on the guest list have been making their way to the summer garden party at the former president's $12 million Martha's Vineyard mansion to celebrate B.O. turning the big 6-0 ... including a pair of powerhouse couples -- John Legend and Chrissy Teigen, and Dwyane Wade and Gabrielle Union ... this according to the New York Times.
Don Cheadle's also arrived, and huge names like Jay-Z and Beyonce, Eddie Vedder, George Clooney and Steve Spielberg are all still expected to attend.