Prepon, 36, showed off her stunning engagement ring as the two made their red carpet debut as a couple at the L.A. premiere of The Girl on the Train on Tuesday, October 4.
Foster, 35, popped the question with a round-cut diamond with a gold band. The Orange Is the New Black actress placed her hand on Foster's arm as they posed for photos at the star-studded event, allowing her ring to shine and be seen. She paired the gorgeous new accessory with Forevermark jewelry.
Us broke the news in July that Prepon and the Finest Hours actor were dating. That month, the two got cozy while hanging out at the Ugly Mug pub in Cape May, New Jersey. "They were really close, talking and laughing," an onlooker told Us at the time.
This will be the first marriage for both. Prepon previously dated Christopher Masterson from 1999 to 2007 and Greek alum Scott Michael Foster from 2008 to 2013.
Foster, meanwhile, most recently dated Robin Wright. They met on the set of their 2011 drama Rampart and got engaged in January 2014. They then called off their engagement in November 2014, but rekindled their romance last January, only to split for the second time in August 2015.
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