Reddit co-founder Alexis Ohanian says he has bought a stake in serial English women's football champions Chelsea.

"I've bet big on women's sports before and I'm doing it again," Ohanian, husband of Serena Williams, wrote on X alongside a news report saying he had bought a 10 percent stake thought to be worth about £20 million ($27 million).

"I'm proud to announce that I'm joining Chelsea FCW as an investor and board member.

"I'm honoured for the chance to help this iconic club become America's favourite Barclays WSL team and much, much more."

The 42-year-old entrepreneur, who married tennis legend Williams in 2017, was previously an investor in US women's football club Angel City FC.

Ohanian has also invested in women's athletics.

Chelsea have just won their sixth consecutive Women's Super League title, becoming the first team to finish a 22-game campaign unbeaten.

They also won the League Cup and will aim to complete a domestic treble when they face Manchester United in the FA Cup final on Sunday.

Ohanian wrote: "These players are rewriting the game. Undefeated season. Eyes on the treble.

"But this isn't just about winning titles. It's about finally matching their talent with the resources, visibility, and respect they deserve.

"I've been right about this before and I couldn't be more excited."

Chelsea said the deal justified the club's decision to sell the women's team to a sister company for a value of £200 million last year to help meet financial sustainability rules.

Aki Mandhar, CEO of Chelsea Women, said: "This is a landmark day in the history of Chelsea Women and for women’s football in Europe and beyond.

"This investment is validation of the club’s past success but more importantly it is yet another proof point in the market of the persistent growth and potential of women’s football."