The pair have worked together on three movies 'Bram Stoker's Dracula', 'A Scanner Darkly' and the upcoming romantic comedy 'Destination Wedding' and Winona claims the pair actually tied the knot for real in 1992 while filming 'Dracula' in Romania.
Speaking to Entertainment Weekly, she said: ''We actually got married in Dracula. No, I swear to god I think we're married in real life.
''In that scene, Francis [Ford Coppola] used a real Romanian priest. We shot the master and he did the whole thing. So I think we're married.''
When Keanu joked: ''It's lovely to see you again'' and added: ''We said yes?'', Winona, 46, reminded him: ''Don't you remember that? It was on Valentine's Day.''
And Keanu, 53, went on to conclude: ''Oh my gosh, we're married.''
Reeves starred as Jonathan Harker in Coppola's movie 'Dracula', with Ryder appearing as his character's partner Mina.
The pair portrayed a couple once again when they reunited for 'A Scanner Darkly' 14 years later in 2006.
Reeves played detective Bob Arctor, who went by the codename Fred, with Ryder appearing as his girlfriend Donna Hawthorne.
In their new movie, Reeves and Ryder portray two unpleasant wedding guests who come together over their mutual misery during the weekend-long event.
Victor Levin has written and directed the film and producer Robert Jones said: ''When comedy is seated in character and truth it's both funny and moving, and on that basis Vic's screenplay is one of the best I've read in a long time.
''Winona Ryder and Keanu Reeves are wonderfully skillful actors and their chemistry on-screen truly brings these irascible characters to life.''