Published: 2019-02-12 04:10:11 BdST
The 28-year-old will join the Turin side in July and become the third Welshman to play for them after John Charles, who played for them from 1957 to 1962, and Ian Rush.
Ramsey has made 256 Premier League appearances since joining Arsenal from Cardiff City in 2008 but he has struggled for a place in the starting line-up under Unai Emery this season and failed to agree on a new deal with the London club in the final year of his contract.
The impasse enabled him to negotiate a pre-contract agreement with foreign clubs since Jan. 1.
The BBC said that Ramsey will earn over 400,000 pounds ($514,040) a week at Juventus, making him the highest-earning British player ever based on basic salary.
Ramsey has made 22 league appearances for Arsenal this season, starting in nine of those and scoring twice, including a splendid strike against Fulham in October that was regarded by many as an early contender for goal of the season.
He had month-long loans to Nottingham Forest and Cardiff City during the 2010-11 season to help him regain match fitness as he recovered from injury.
Ramsey published a statement on Twitter thanking Arsenal's "loyal and supportive" fans.
"You welcomed me as a teenager and have been there for me through all the highs and lows I've encountered during my time at the club," he said. "It is with a heavy heart that I leave after 11 incredible years in North London."
Arsenal said in a statement that Ramsey had made a "fantastic contribution" to the club.
"He has always been a consummate professional and will always have a special place in the hearts and memories of Arsenal fans around the world," it said.