Chelsea have confirmed the signing of United States women's national team defender Naomi Girma for a world record fee on a long-term deal from San Diego Wave, as first reported by ESPN.

The deal sees Girma become the first player to break the $1 million mark in the women's game.

ESPN revealed on Jan. 16 that Chelsea were the leading contenders to sign Girma, with initial interest from Lyon and Arsenal, before confirming that the west London club had won the race for the 24-year-old's signature. It is understood that Arsenal were not among the final candidates.

The fee surpasses the previous record deal of $767,600, paid by NWSL side Bay FC to sign Zambia forward Racheal Kundananji from Madrid CFF in February 2024.

Girma was unveiled on the pitch at Stamford Bridge ahead of Chelsea's Women's Super League (WSL) clash with Arsenal on Sunday.

"I'm so happy and really excited to be here. It doesn't feel real," Girma said in a statement.

"There are a lot of things about Chelsea that made me want to come here -- the culture, the winning mentality, staff and players. It's a top environment to learn and grow in. Right now, that's what I'm looking to do. It was an easy choice for me."

Girma was instrumental in helping the USWNT achieve gold at the Paris Olympics last summer.

Former Chelsea manager and reining USWNT coach Emma Hayes has said Girma is "the best defender I've ever seen. Ever. I've never seen a player as good as her in the back."

Girma was under contract with the NWSL's San Diego Wave until 2026. She has 44 caps and has scored twice for her country after debuting in 2022. In 2023, she was named U.S. Soccer's women's player of the year.

Chelsea are six points clear at the top of the WSL table.

Information from ESPN's Tom Hamilton contributed to this report