Ballard, who has been an integral part of the Black Cats' successful return to the Premier League this season, has agreed a new contract on Wearside that runs until the summer of 2029, with Sunderland having the option to extend the agreement by a further 12 months.
Since arriving on Wearside in June 2022, the 26-year-old centre-half has made 114 senior appearances for Sunderland, scoring eight goals.
He has been the subject of ongoing transfer speculation linking him with a number of clubs, both at home and abroad, so his new deal is a major boost to the Black Cats.
"I’m absolutely delighted to have signed a new contract," said Ballard, who started his career in the youth ranks at Arsenal. "From the moment we began talks, it felt like an easy decision, and I’m happy to be extending my time at the club.
"Achieving promotion last season was incredible, and I feel very fortunate to have played a part in some special moments in the club’s recent history.
"My aim this season was to stay in the team, compete every day, and keep working hard to contribute. Hopefully, I can continue improving and help drive the club forward for many years to come.”
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Ballard’s time on Wearside includes one of the most iconic moments of all time at the Stadium of Light – the last-minute winner in last season's play-off semi-final against Coventry that sent the Black Cats to Wembley.
Imperious at the back throughout the last four seasons, the Northern Ireland international has successfully established himself as one of the most dominant defenders in the Premier League this term.
Alongside his team-mates, Ballard has played a central role in Sunderland claiming eight clean sheets in 27 league matches, while also registering four top-flight goal contributions.
“Dan represents both the legacy and the future of Sunderland AFC," said director of football Florent Ghisolfi. "He embodies our identity through his professionalism, consistency, and spirit.
"He has grown into a Premier League defender, but just as importantly, he has become a leader within our dressing room.]
"We are proud that he believes in our purpose and our ambition. His commitment to Sunderland is a powerful message about who we are and what we intend to build.”