Berbatov will wear the number 15 at Stade Louis II, where he will stay until the end of the season, when his contract with the Cottagers expires.
Speaking about the addition of Berbatov, Monaco vice-president Vadim Vasilyev said: "Dimitar will bring us all his experience and talent.
"His coming is of course connected to Radamel Falcao's injury. He played in big clubs such as Manchester United and he's a big striker.
"We still have two competitions to play and he will be an asset with Emmanuel Riviere, Valere Germain and Anthony Martial. He has a different profile than our other forwards."
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