But while the sports royalty couple made the announcement to a combined audience of nearly 6.5 million people, Vonn and Woods requested they be granted privacy by the public with Woods saying they wanted to live "as an ordinary couple."
Woods, 37, and Vonn, 28 -- both divorced -- said their relationship sprouted from a friendship over the past few months, The New York Times reported.
The newspaper said Woods wrote on his Facebook page not only has his golf game been great with PGA Tour wins at Torrey and Doral, but "something nice that's happened off the course was meeting Lindsey Vonn."
"Lindsey and I have been friends for some time, but over the last few months we have become very close and are now dating," Woods said. "We thank you for your support and for respecting our privacy. We want to continue our relationship, privately, as an ordinary couple and continue to compete as athletes."
He also posted four photos of them.
Vonn allowed in her Facebook post their relationship "wasn't a well-kept secret."
"But yes, I am dating Tiger Woods," she said. "Our relationship evolved from a friendship into something more over these past few months and it has made me very happy. I don't plan on addressing this further as I would like to keep that part of my life between us, my family and close friends. Thank you for understanding and your continued support!"