The France international, who was a reported target of Liverpool this summer, was keen to leave PSG to earn more playing time ahead of Euro 2016.
Digne made just 21 starts in all competitions for the French champions last season and Roma have an option to make the player’s stay permanent next summer.
A statement from Roma confirmed the deal: “The defender arrives from the French club on a temporary deal until June 30, 2016 in exchange for a loan fee of 2.5million euros.
“The agreement includes an option to make the move permanent ahead of the 2016-17 season.”
The 22-year-old left-back began his professional at Lille and was handed his first-team debut at the club in 2011 by current Roma boss Rudi Garcia.
He moved to PSG two years ago and has since won two Ligue 1 titles and a Coupe de France.
Digne is under contract with PSG until June 2018 and is delighted to have arrived to Rome.
“I chose AS Roma because it’s a legendary club with a big history,” he said on the club’s official website. “I know that in this city and at this club there’s everything you need to have success.”