She said in the poem, posted from her verified Reddit account, that Ohanian proposed at the place they first met during a surprise trip to Rome.
Williams wrote: “I came home/A little late/Someone had a bag packed for me/And a carriage waited. Destination: Rome/To escort me to my very own ‘charming/Back to where our stars first collided/And now it was full circle/At the same table we first met by chance/But by choice/ Down on knee/He said 4 words/And I said yes.”
The couple have been dating since at least late 2015, but have kept their relationship quiet, with the exception of a few Instagram posts.
Four weeks ago, Williams posted a photo of the couple at a costume party. Within minutes of the engagement announcement, comments on the photo were dominated with congratulatory messages and emojis.
Ohanian shared Williams’s Reddit post on his Facebook page with the message: “she said yes”. He also commented on her Reddit thread, writing: “And you made me the happiest man on the planet”.
Williams is widely regarded one of the greatest tennis players of all time and has won 22 major singles titles and a further 16 in doubles. She will aim to win her seventh Australian Open title in Melbourne next month.
Both she and her sister Venus arrived in Auckland on Friday for a tournament leading up to the Open.
Venus Williams said she had to keep a lid on the news of her sister’s engagement after getting the early word.
“I might just be her big sister, I might know these things,” she said.
This article was written by Amanda Holpuch in New York, for theguardian.com on Thursday 29th December 2016 20.56 Europe/Londonguardian.co.uk © Guardian News and Media Limited 2010