Travolta posted on Instagram: "My beautiful wife Kelly has lost her two-year battle with breast cancer. She fought a courageous fight with the love and support of so many."
The couple had been married for nearly 29 years. Preston's career included roles in Twins, From Dusk Till Dawn, Jerry Maguire and The Cat in the Hat.
She also collaborated with her husband on Battlefield Earth and Old Dogs.
In his post, Travolta thanked the health workers who had looked after his wife "as well as her many friends and loved ones who have been by her side".