"Fiorentina and Villarreal confirm they have reached an agreement for the sale of Giuseppe Rossi subject to the signing of the contract by the player," the Serie A club said.
According to media reports, Italian international Rossi is to sign a five-year deal and will cost an initial fee of 11 million euros plus add-ons.
Rossi came through the ranks at Serie A club Parma after starting his youth career in his birth nation of the US with Clifton Stallions Soccer Club.
Manchester United recruited the young striker in 2004, but despite a prolific spell for their academy side, he would only make five league appearances for the Red Devils, scoring one goal.
A return to Parma on loan was more fruitful, with the 5'8" forward netting nine times in 19 games before he switched to Villarreal in a permanent deal in 2007.
Rossi has scored 54 goals in 136 games for the Spaniards, who were relegated from the top flight last season, when the Italian international was sidelined with a pair of major injuries to the anterior cruciate ligament of his right knee.
He has won 27 caps for Italy, scoring six goals, and is expected back in action in March.