"It's been going on for a few weeks now."
West, who is in the middle of a divorce with his wife of seven years Kim Kardashian, was seen walking side-by-side with Shayk on the sprawling Provence property, Villa La Coste, in the French countryside.
It's the rapper's first relationship since Kardashian, the mother of his four children, filed for divorce in March.
Kardashian, 40, paid loving tribute to her soon-to-be ex-husband on Instagram yesterday, declaring "Love u for life".
Neither West or Kardashian have released an official comment about their split.
Shayk shares a child with her Oscar-nominated ex Cooper, a daughter, Lea De Seine, born in 2017.
Shayk broke her silence on their split for the first time last year, speaking to British Vogue.
"I think we've been very lucky to experience what we had with each other," Shayk said of Cooper. "Life without B is new ground."
She added: "I have a strong personality and I definitely know what I want, and I think some men are scared of that."
Despite their recent union, West and Shayk go way back.
The Victoria's Secret model appeared in West's 2010 music video for his song Power, and walked the runway for his Yeezy fashion line at Paris Fashion Week in 2012.
