The Armenian’s contract with Arsenal has been terminated by mutual consent, allowing him to join Roma for free.
Mkhitaryan, 31, spent last season on loan in the Italian capital and made his mark on the team.
In 16 league starts, he had an impressive return of nine goals and five assists for the Giallorossi.
He joined Arsenal from Manchester United in 2018 and bagged a hat-trick of assists on his debut against Everton.
The nine-time Armenian Footballer of the Year played for Shakhtar Donetsk and Borussia Dortmund before his move to England.