The defender, who has over 50 top-flight appearances to his name, has signed a deal at the principality club which keeps him at Monaco until June 2023.
The 22-year-old is highly rated and expected to take the full step up into the France international side before too long.
Henry hopes he will be able to shore up his leaky defence and help push the side away from the relegation places in the league. Monaco are currently second bottom five points from safety.
Club vice president Vadim Vasilyev said:
Welcome to Fodé Ballo-Touré at AS Monaco. He is a talented young player who, like his team, had a good first half of the season and will continue to improve.
"His arrival, along with that of Naldo, should allow to intensify the competition and thus strengthen the workforce
I was quickly convinced by the AS Monaco project and the prospect of working with Thierry Henry.
"I am eager to learn from him, his experience, his knowledge, but also to meet my new teammates to get into the thick of it
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