A family close to the couple confirmed that they have been separated since May, reports People.
The announcement comes after McGregor was spotted kissing his co-star Mary Elizabeth Winstead at a West London cafe last week.
The 'Star Wars' actor and the 32-year-old actress play on-screen lovers in the US telly show 'Fargo.'
Winstead split from her husband, Riley Stearns, in May after seven years of marriage.
McGregor, 46, met Mavrakis on the set of the British TV crime series 'Kavanagh QC.'