The Manchester United star sent two private Instagram messages to 23-year-old Tina Stinnes.
The 30-year-old Belgian who once sent n-ked pictures of himself to a French model was put in his place on this occasion by Matthew Mawhinney.
He uploaded the footballer's messages which read 'Hey' and 'How are you?' with the instruction: 'Fellaini get out of my girlfriend's DMs.'
Tina first found fame on Made in Chelsea dating Jamie Lain and Alex Mytton before a romance with Spencer Matthews but began dating Matthew, who is the son of Baroness Scotland, this year.
She lasted 21 days in the villa when she appeared on the second series of ITV2's Love Island in 2016.
Midfielder Fellaini was last known to be dating 38-year-old Victoria Bonya, the Russian Playboy model.