The deal sees the highly rated 17-year-old sign her first professional contract having previously been on the books of Arsenal in their youth ranks, with her set to wear the number 30.
Mace made her senior debut for the Gunners in September 2020 against Tottenham Hotspur in the Vitality Women’s FA Cup quarter finals, replacing captain Kim Little late on in a 4-0 victory.
Figuring a handful more times for the first team, including against Chelsea and London City Lionesses in the Continental Tyres League Cup and in FA WSL fixtures against Brighton & Hove Albion and Spurs, the teenager joined Birmingham City in February 2021.
Eligible to play for both sides under dual registration, she played eleven times in total for the Midlands side, scoring twice against West Ham United and Reading.
Also an international with England at various age groups and currently at Under-19 level, she made her debut for the Under-15s in October 2017 against Scotland, captaining the side that day, before scoring her first goal for her homeland against Switzerland soon after.
And ahead of the upcoming 2021/22 season, Mace has put pen to paper on a three-year deal with City that will keep her at the Club until the summer of 2024.
Speaking about her move, she said: “I'm so happy and excited to join Manchester City.
“As a 17-year-old, it's the biggest moment in my short career so far. I've got so much to learn and develop in my game and I feel this is the best environment for me to achieve my dreams.
“Amazing players, an amazing Club and amazing coaches! I'd also like to thank Arsenal for all they have done for me to get me to this point."
Head Coach Gareth Taylor added: "We're thrilled to have added Ruby to our squad here at Manchester City - she's a talented player who we feel has a very bright future ahead of her.
"She's already proven that she can make her mark in the Barclays FA Women's Super League and we're really looking forward to working with her in the coming seasons.
"We've had a number of young players make their mark here at City in recent years and hopefully Ruby will be the next one in that long line of success stories."
Manchester City Women Managing Director Gavin Makel concluded: “We're delighted to welcome Ruby to the Club, who is one of the most exciting young talents in England.
“We know the potential that she has, and we are looking forward to working with her to develop that further.”
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