They began dating in 2004, following her split from John Byrne who she shares twins Honor and Xavier.
And Tilda Swinton, 57, and Sandro Kopp, 40, looked loved-up as they spent time together at the Venice Film Festival on Monday.
The couple looked relaxed as they strolled side-by-side through the streets of the Italian city, and the actress looked ethereal in a ruched white top.
Loved-up: Tilda Swinton, 57, took a stroll with her beau Sandro Kopp, 40, as they attended the Venice Film Festival on Monday
The Okja star paired her stylish shirt with a peach chiffon skirt, which cascaded over her trim legs.
Stepping out in a pair of stripped yellow slip-on shoes, while she shielded her eyes with a pair of stylish cat-eye shades.
Tilda’s blonde locks were slicked back into a stylish up-do, and wore minimal touches of make-up to rely on her natural look.
Stunning: The Okja star looked ethereal in a ruched top which she paired with a peach chiffon skirt, that cascaded over her trim legs
Sandro put on a colourful display for their outing, donning yellow top with pink sleeves over a pair of blue shorts.
The visual artist completed his look with a pair of black slip-on shoes, which he wore with pink socks, while keeping a low profile in aviator shades.
His salt-and-pepper locks were brushed into a tousled hairstyle, and he looked dapper with his bushy beard.
Finishing touches: Stepping out in a pair of stripped yellow slip-on shoes, while she shielded her eyes with a pair of stylish cat-eye shades
The actress is in Venice for the premiere of her horror film Suspiria, that is in competition for the main prize of the festival.
According to the studio, the film is about ‘a darkness [that] swirls at the center of a world-renowned dance company, one that will engulf the artistic director, an ambitious young dancer, and a grieving psychotherapist.
‘Some will succumb to the nightmare. Others will finally wake up.’
The film stars Tilda, Dakota Johnson, Mia Goth, Lutz Ebersdorf and Chloe Grace Moretz.
Standing out: Sandro put on a colourful display for their outing, donning yellow top with pink sleeves over a pair of blue shorts
50 Shades Of Grey star Dakota plays an ‘ambitious young dancer’ studying under a character played by a haunting Tilda.
The doctor in the film is allegedly played by real life doctor Lutz Ebersdorf but rumors surfaced that it might actually just be Tilda Swinton in elaborate makeup.
However, according to Indie Wire, Suspiria’s executive producer Stella Savino insists the character isn’t played by Swinton and that the doctor is real, with no acting experience.
Suspiria is a feature remake of a 1977 short film of the same name, it’s directed by Luca Guadagnino who helmed last year’s best picture Oscar nominated romance Call Me By Your Name.
Clashing colours: The visual artist completed his look with a pair of black slip-on shoes, which he wore with pink socks, while keeping a low profile in aviator shades