Macario, who has 17 international caps, scored 23 goals in 33 games for Lyon, helping them win a French title and the Women's Champions League.

"Cat is one of the most intelligent, creative attacking players in the world," said Blues manager Emma Hayes.

"She brings a great deal of flair, European experience, and an unbelievable winning mentality. I think our fans will really love her."

Brazilian-born Macario, who is regarded as one of the most exciting prospects in the women's game, became the first American to score in a Women's Champions League final during Lyon's 3-1 win over Barcelona in 2022.

However, she has not played since rupturing her anterior cruciate ligament just over a year ago, in the final game of 2021-22 Division 1 Feminine and has already ruled herself out of this summer's World Cup.

Macario's arrival in at Chelsea comes with captain Magdalena Eriksson and forward Pernille Harder leaving the club when their contracts expire this summer.