“Who the Heck Is Alexis Ohanian, and Why Would Serena Williams Want to Date Him?” Slate magazine asked in a headline last year.
Mr. Ohanian is a co-founder of Reddit, and, as of Thursday, Ms. Williams not only wants to date him, but plans to marry him.
Ms. Williams, the tennis superstar, announced her engagement to Mr. Ohanian on Reddit, the website that claims the label “the front page of the internet.”
The Reddit post featured a drawing of Snoo, the site’s mascot, dressed as Mr. Ohanian and kneeling with a diamond in its hand. A female Snoo, styled after Ms. Williams and wearing a tennis skirt, Nike top and headband, floated above him with a smile on her face.
Above the picture was the headline, “Future Mrs. Kn0thing.” It was a nod to the site and its community: Mr. Ohanian has long gone by the handle Kn0thing.
In free verse, Ms. Williams, whose account is verified on the site, described the proposal on the “isaidyes” subreddit, which is dedicated to engagement stories.
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 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
Mr. Ohanian chimed in in the comments: “And you made me the happiest man on the planet.”
A spokeswoman for Ms. Williams, Kelly Bush Novak, said that a wedding date has not been set. Ms. Williams and Mr. Ohanian had known each other for some time before they started dating last fall, she said.
Ms. Williams, 35, is one of the greatest American athletes active today, and is the highest-paid female athlete in the world. She won her first Grand Slam singles title at 17 in 1999, and this year won her 22nd. She has spent more than 300 weeks at No. 1; a recent run of 186 consecutive weeks in the top spot ended in September.
Ms. Williams has not played a match on tour since losing in the semifinals of the United States Open in September. She plans to open her tennis season next week in Auckland, New Zealand.
Though Mr. Ohanian, 33, is significantly less well-known by the general population, he too has risen to the top of his field since starting the site that would become Reddit with his college roommate, Steve Huffman, 11 years ago.
The site was pitched to the start-up incubator Y Combinator and was acquired by Condé Nast just 16 months after it began. In 2010, Mr. Ohanian joined Mr. Huffman at another company, Hipmunk. In 2013, he wrote a book about the power of the internet called “Without Their Permission.”
Mr. Ohanian also posted the news on his Facebook page.
In an interview with Vogue in July, Ms. Williams was asked to identify the most romantic thing a man had ever done for her.
“It hasn’t happened yet,” she replied
On Twitter, Mr. Ohanian had called the interview “pretty great.
A user replied to him, and to Ms. Williams: “Alexis, I think you need to get on that most romantic thing.”