In the series, the raven-haired star is mourning the loss of her new husband Matthew Crawley, but in real life she is being romanced by handsome financial PR John Dineen.
The 31-year-old actress, currently in the Italian city for its famous film festival, was spotted sharing kisses with her new boyfriend. The pair's blossoming romance began a few weeks ago, when they were introduced by mutual friend Allen Leech, who plays chauffeur Tom Branson in the show.
According to Mail Online, Ireland-born John – also 31 – lives close to the actress in Clerkenwell, Central London.
A friend of the senior director with FTI Consulting tells the publication: "He is very private and softly spoken but he has really been taken by Michelle.
"Friends have joked that they must have also been drawn together because of their Irish connections."
Michelle hails from Essex, but her father Michael was born in Dublin. Meanwhile John was brought up in Waterfall, near Cork, where his parents run a farm.