Watts comes down to the third tier having been on the books of WSL2 side Saints for the past decade, since joining the club at U10 level.
The Christchurch defender signed her first professional contract with Bournemouth’s neighbours last summer, and left the club after last season after the expiry of her contract.
She made 17 senior appearances for Saints, with nine in WSL2 in the 2025/26 season, as Southampton finished fifth in the second tier.
The 19-year-old told afcb.co.uk: “I am delighted.
“The club has massive ambitions for the women’s game and for the future. I can’t wait to be on that journey and develop with the team.
“It was really important for me to go to a team where the ambition is there, so that I can pave my pathway and go with them.
“Growing up, I went to Vitality Stadium to watch a few games with my dad and had a few AFC Bournemouth kits when I was younger.
“It’s my local team, so I have seen the men’s team grow and the women’s team going through the leagues and progressing.
“I can’t wait to get myself out there, get some minutes under my belt and show who I am as a player on the pitch.
“I am excited to go on the journey with the Cherries.”
Head of women’s football, Bruce Suraci, added: “We’re really pleased to get Issy’s signing across the line and excited to see how she develops here.
“She has a strong athletic profile, the ability to attack and defend in 1v1 situations, and she fits well with our playing philosophy.
“Most importantly, Issy has outstanding character.
“She is a consummate professional in her attitude and highly motivated to progress.
“We were particularly impressed by her public disclosure of her experience of living with autism.
“As a club, we pride ourselves on our approach to working with neurodivergent individuals, and we believe we can work together with Issy to help unlock her full potential.
“As a local player from Christchurch, she also has the opportunity to become an outstanding role model for young girls who support AFC Bournemouth, and we are looking forward to the future with her.”
Watts joins the ten retained players in the Cherries squad for the upcoming season.
