"Cheers to a life full of love, happiness, adventure, and great purpose, Mrs. Hefner. I love you dearly and very much look forward to planning our wedding celebrations in the months ahead. I love you, Scarlett."
The couple have been together for over six years, with Cooper popping the question in 2015.
British star, Scarlett – who has also appeared in The Vampire Diaries and Falling Skies – also took to Instagram to share the happy news.
"I love you Cooper. I am proud to stand by your side, as your partner, your friend, and your wife. I cannot wait to continue building a life together. My heart is so full and I am so grateful for our love," she gushed.
Cooper, whose mother is Hugh’s second wife ex-wife and 1989 Playmate of the Year Kimberley Conrad, took over the Playboy Enterprises in 2016, less than a year before his father’s death.
The businessman confirmed to The Hollywood Reporter at the beginning of the year that he had stepped down from Playboy Enterprises and launched his own media company.
At the time, he had planned to call it HefPost, but on his social media accounts he now lists himself as the CEO of StagDaily, which is expected to launch in 2020.
Cooper and Scarlett have confirmed they will be having a larger wedding ceremony with family and friends at a later date.