The actors - who play Harry and Ron respectively - walked the red carpet at the launch of the 'Wizarding World Of Harry Potter' theme park at the Universal Studios Resort in Orlando.
They were joined by co-stars Tom Felton (Draco), Bonnie Wright (Ginny) and Oliver and James Phelps (George and Fred Weasley).
Author JK Rowling and castmates Michael Gambon (Dumbledore), Warwick Davis (Professor Flitwick) and Matthew Lewis (Neville Longbottom) were also present.
According to the Daily Mail, co-star Emma Watson (Hermione) was unable to attend because of university commitments, but she was photographed getting a preview tour of the attraction last month alongside castmate Robbie Coltrane (Hagrid).
Entertainment Weekly reports that guests were treated to a fireworks display and performance by the Frog Choir Of Hogwarts, led by John Williams and the Orlando Symphony Orchestra.
The park opens to the public tomorrow.