Serena Williams, the tennis star, announced on Thursday that she was engaged to Alexis Ohanian, a co-founder of Reddit, the social messaging site.
The 22-time singles major champion and Mr Ohanian, 33, began dating last autumn, but had largely kept their romance private.
A spokesman for Mr Ohanian confirmed he proposed while the couple were on holiday in Rome.
Williams, 35, posted a poem on Reddit to announce the news.
“I came home/A little late/Someone had a bag packed for me/And a carriage awaited,” she wrote.
“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/This time he made it not by chance/But by choice/Down on one knee/He said 4 words/And/r/isaidyes.”
Williams, who has won Wimbledon seven times, had been romantically linked to a number of athletes and other celebrities before she and Ohanian began dating.