Financial details of the deal were not disclosed, but British media reported that PSG activated an 8.5 million pounds ($11.46 million) release clause for the left-back.
Digne returns to the French capital 11 years after leaving PSG, having spent two seasons at the club between 2013 and 2015, during which he won two Ligue 1 titles, a French Cup and two League Cups.
"I am very honoured to be returning to Paris St Germain following the wonderful experience I had here more than 10 years ago," Digne said in a statement.
"I cannot wait to start this new chapter and put all my experience at the service of the team."
Digne began his professional career at Lille before joining PSG and later spending a season on loan at Roma.
Digne moved to Barcelona in 2016, making 46 appearances for the Spanish giants over two seasons and adding a La Liga title, two Copa del Rey trophies and a Spanish Super Cup to his list of honours.
He joined Everton in 2018 and spent four years with the Premier League club before moving to Aston Villa.
The 33-year-old spent four-and-a-half seasons at Villa Park, where he became a key player under manager Unai Emery and helped the club win the Europa League in 2026.
A France international since 2014, Digne has earned 64 caps and represented his country at two World Cups, most recently helping Les Bleus reach the semi-finals in 2026.
PSG begin their Ligue 1 campaign against Rennes on August 23.