West Ham have signed Maz Pacheco following the left-back's departure from fellow Women's Super League club Reading.
It was announced last month that the 21-year-old would be leaving Reading at the end of her contract.
"She is a great attacking full-back," said manager Matt Beard, who gave Pacheco her senior debut at Liverpool in 2015.
"I'm looking forward to continuing her development as a player here."
He added: "We've got ourselves a young, English, elite player. The ambition for her now is to get into this West Ham team, play regularly, and hopefully we can help her fulfil her international ambitions too."
The Hammers signed Australia international goalkeeper Mackenzie Arnold on Thursday.