The fee for the 19-year-old, who is a left-footed attacker primarily deployed on the right flank, remains undisclosed.
An England Under-21 international, Dibling arrives at Goodison Park after a breakthrough season on the south coast.
He featured in 33 Premier League matches during the 2024–25 campaign, the fifth-most appearances in the Southampton squad, underlining his rapid development since making his first-team debut at just 17 in August 2023.
The move makes him David Moyes' eighth addition of a busy summer transfer window. The Everton manager has overseen the permanent arrival of Charly Alcaraz and brought in Thierno Barry, Mark Travers, Adam Aznou, Kiernan Dewsbury-Hall, Tom King and Jack Grealish, the latter joining on loan, as part of a major squad rebuild.
"I'm buzzing to sign. I felt the club already, even before I was in the building, just from social media and from people telling me about the club. I've never been so excited to play football and I'm just ready to get going," Dibling told EvertonTV.
"I think it's the perfect match because of where the club is right now. Obviously with the new stadium, the fans here are unreal and it has a family feel to it. I think it was the perfect fit and was a no-brainer to join.
"I think I've come to Everton at the perfect time and hopefully I can be here for many years.
"[The Brighton win] gave me a feel for the club. It looked unbelievable. I also played in the last Men's game at Goodison. It was so loud. I was looking around and thinking, 'This is quality'. That was a really good insight for me into what it's like here with the fans and the atmosphere they can create.
"There's no better feeling than when you're doing well in football and to feel that love from the fans is one of the best feelings ever. I'm excited to play here."
Jack Grealish has been hailed as "better than I thought he was" by Everton boss David Moyes after another standout performance from the on-loan Manchester City winger helped Everton to a thrilling 3-2 victory over Wolves at Molineux.
Bruno Fernandes and Wilson Isidor's late goals secured dramatic wins for Manchester United and Sunderland, while Jack Grealish's brilliance helped Everton edge Wolves in Saturday's Premier League action.
West Ham have officially announced the signing of Portuguese midfielder Mateus Fernandes from Southampton in a deal worth over 40 million pounds.
Leeds United have kicked off their Premier League campaign with a gritty 1-0 victory over Everton at Elland Road, thanks to a dramatic late penalty from substitute Lukas Nmecha.
