Matildas' defender Carpenter leaves Lyon for Chelsea
Carpenter, who has agreed a four-year contract, will be reunited with head coach Sonia Bompastor, who took charge of Lyon in 2021 before guiding Chelsea to a treble-winning season in her first campaign last year.
Carpenter moved to Lyon in 2020 and in the five years since has won two Champions Leagues, four French championships and the French Cup.
"I'm really excited about this new challenge, it's a new adventure," she told the Chelsea website.
"It feels like the right move for me, and I can't wait to get started and give my all for this club.
"I'm very proud to join such a big club, one of the biggest in women's football. Chelsea have enjoyed so much success in England, and I'm delighted to now be a part of it."
Carpenter, who hails from Cowra, a small town in New South Wales, began her senior career at the age of 15 and became the youngest woman ever to play football at the Olympics at Rio 2016, aged 16. She went on to play at the subsequent Games in Tokyo and Paris.
Aged just 18, Carpenter secured a move to the US with Portland Thorns before moving on to Lyon.
Last month Carpenter married her Lyon teammate Danielle Van de Donk but the Dutch midfielder, 33, will now be a rival in the Women's Super League having joined London City Lionesses - owned like Lyon by the American businesswoman Michele Kang - on a free transfer at the end of June.