Arsenal said Mead “is set for an extended period on the sidelines” after confirming the extent of her injury, and will set out a timetable for surgery in the coming days.
The 27-year-old wrote on her Twitter feed: “Obviously heartbroken by the news of my injury, unfortunately these things are part of the game.
“But I’ll be working hard to be back on the pitch as soon as possible. For now I’ll be Arsenal and England’s biggest fan. Thanks so much for all the love and support.”
A statement from Arsenal on Tuesday said: “We can confirm that Beth Mead suffered a ruptured anterior cruciate ligament in our match against Manchester United at Emirates Stadium on Saturday.
“Unfortunately, this means that Beth is set for an extended period on the sidelines. She will see a surgeon in the coming days, after which further details on timescales will be established.
“Everyone at the club will now be supporting Beth and working hard to get her back on the pitch as soon as possible.”
Mead has scored three goals in the WSL and two in the Champions League for the Gunners this season, which follows her starring role in England’s triumph at the Euros during the summer.
She was named player of the tournament and claimed the Golden Boot with six goals, and last month was Ballon d’Or runner-up behind Spain’s Alexia Putellas.
England will be back in major tournament action next summer at the World Cup taking place in Australia and New Zealand, from July 20.
A message of support for Mead on the Lionesses’ official Twitter said: “We know you’ll come from this back even stronger.”