The two-time Oscar winner revealed the happy news in an Instagram post on Tuesday.
“Went on a hike and this happened! I am so happy to share with you all, the engagement to my dear Ruben. #Engaged,” the 41-year-old penned alongside a snap of the couple kitted out in their hiking gear, along with several heart emojis.
The starlet also shared a photo of the stunning ring, which screamed Hollywood!
A source told People that the tennis coach and financial advisor popped the question over the weekend at the BNP Paribas Tennis Open in Palm Springs.
The couple began dating in July 2015 and they made their first official appearance on the red carpet together in December.
This will be Hilary's second time down the aisle. The pretty brunette was previously married to Chad Lowe for ten years. They married in 1997 and divorced in 2007.