Ballard has signed a three-year deal at the Stadium of Light, with a club option of a further year, after making 31 Championship appearances on loan at Millwall last season.
The 22-year-old became the Black Cats second signing of the summer, after Leon Dajaku’s move from Union Berlin was made permanent due to a clause being triggered in his loan deal.
Making the step up to the Championship will be challenging, though, with many teams operating with bigger budgets and some having the advantage of Premier League parachute payments.
Here are all the signings that have been made by Championship clubs so far this summer:
1. Birmingham
IN: Finley Thorndike (free, Aston Villa) | OUT: Fran Villalba (Sporting Gijon), Jeremie Bela (released), Renedi Masampu (released), Kristian Pedersen (FC Koln), Kane Thompson-Sommers (released), Connal Trueman (released), Yoane Zohore (released), Ivan Sanchez (Real Valladolid) Photo: Nathan Stirk
2. Blackburn
IN: Ethan Walker (free, Preston North End) | OUT: Joe Rothwell (Bournemouth), Bradley Johnson (released), Jacob Davenport (released), Harry Chapman (Bradford), Luke Brennan (released), Connor McBride (released), Sam Durrant (released), Joe Nolan (released), Antonis Stergiakis (Panetolikos), Darragh Lenihan (Middlesbrough) Photo: Alex Livesey
3. Blackpool
IN: None | OUT: Cameron Antwi (released), Ryan Grant (released), Johnny Johnston (released), Matthew Liptrott (released), Charlie Monks (released), Ethan Robson (MK Dons), Sky Sinclair (released), Grant Ward (released) Photo: Clive Brunskill
4. Bristol City
IN: Mark Sykes (free, Oxford), Kal Naismith (free, Luton), Kane Wilson (free, Forest Green) | OUT: Callum O'Dowda (Cardiff), Louis Britton (released), Kasey Palmer (Coventry), Robbie Cundy (Barnsley), Saikou Janneh (Cambridge) Photo: Marc Atkins