The Bristol-born 27-year-old, who qualifies for the Azzurri through his grandfather, boasts 13 caps and is part of Kieran Crowley’s squad for the current Six Nations championship.
He is currently playing for United Rugby Championship side Benetton Rugby but will move to Saints ahead of next season to compete with the likes of Alex Mitchell and Tom James.
“I’m really excited to sign for a huge club in Northampton Saints and return to the Gallagher Premiership,” said Braley.
“My experience over in Italy has been fantastic and I feel like I have grown as a person and a player, but I am ready for a return to England and to challenge for silverware with Saints.
“Northampton players are encouraged to express themselves on the field and I love the way the team plays.
“It’s clear to me there’s a great environment to develop as a player at Franklin’s Gardens, and there are exciting times ahead with the coaching group that has been put in place for next season.
“I remember how passionate the Northampton supporters are from my time in the Premiership, and I hope I can do them proud when I pull on a black, green and gold jersey next season.”
After coming through the Academy at his hometown club, Bristol Bears, Braley made a West Country switch to Gloucester Rugby in 2014.
He went on to notch up more than a century of appearances for the Cherry & Whites.
His form at Kingsholm saw him selected for Italy ahead of the 2019 Rugby World Cup – Braley made his full international debut in a warm-up match against Ireland before featuring twice at the tournament in Japan against Canada and South Africa.
A move over to Italy with Benetton Rugby beckoned, with Braley moving to Treviso in 2020 to play his club rugby alongside a number of his international team-mates.
There he was part of the side which claimed a surprise victory over the Bulls in the 2021 Pro14 Rainbow Cup final – a historic first success in an international competition for any Italian club.
The No.9 was also an England age-group international from Under-16 level upwards, and skippered the successful defence of England Under-20s’ Junior World Championship back in 2014.
Saints attack coach Sam Vesty said: “Callum is someone who has really impressed us with his all-round quality.
"His basics are strong and his ability to get the ball up and moving quickly suits the way we play.
“He’s also got superb leadership qualities, playing at the highest level internationally, and boasts experience across multiple leagues.
“So we’re confident he can add a lot to our young group of scrum-halves who are all already pushing each other to improve constantly.”