Wales midfielder Angharad James will join National Women's Soccer League (NWSL) side North Carolina Courage on a two-year contract.
The 26-year-old has been with Reading since July 2019 but is in the final year of her contract with the Women's Super League (WSL) club.
James, from Haverfordwest, has won 83 Wales caps and scored two goals.
"I move to North Carolina in the knowledge that I gave everything to Reading," James said.
"I'll continue to do so while I'm still here. Thank you all, from the bottom of my heart."
Both clubs say James will move "on a date mutually agreed upon by the Courage and Reading that will be announced at a later time".
Reading's final WSL fixture is on 9 May. The NWSL's Challenge Cup begins on 9 April, while the 2021 league season is set to start on 15 May.
James made her Wales debut as a 17-year-old against Scotland in October 2011 and has become a mainstay of her national side.
She joined Arsenal Ladies' Academy in 2010 at the age of 16, before heading to Bristol City two years later. She went on to play for Notts County, Yeovil Town and Everton before joining Reading.
"I want to take this opportunity to say a massive thank you to everyone at Reading for making me feel so welcome during my time here," James told the club website.
"I can't thank Kelly (manager Chambers) and her staff enough. I only have praise and admiration for them, for giving me the opportunity to grow and express myself on the pitch, they have been instrumental in my development."
North Carolina Courage took the NWSL league title in 2018 and 2019, and are three-time Shield winners.
"Angharad is a true competitor and will thrive in our environment," NC Courage head coach Paul Riley told the club website.
"She is intelligent, tough and has the ability to improve all of those around her. She will be a stabilizing force in our midfield and her understanding of tactics will help us adapt our formations for the new season."