Accompanying the image, the tennis star shared a poem detailing the romantic proposal.
Titled, I said Yes, Williams writes: 'I came home a little late, someone had a bag packed for me, and a carriage awaited — destination, Rome.
'To escort me to my very own charming, back to where our stars first collided, and now it is full circle. At the same table we met by chance, this time he made it not by chance, but by choice.
'Down on one knee, he said four words and I said yes.'
Responding to William’s poem, Ohanian wrote on social media, ‘You made me the happiest man on the planet.’
The engagement comes as a surprise to many – Williams and Ohanian have kept their love off of social media.