The 19-year-old has repeatedly been linked to the Reds in recent weeks and has signed a four-year contract with the Barclays Premier League club.
He will go straight into the Merseysiders' first-team squad, joining fellow summer arrivals Andrea Dossena, Diego Cavalieri and Philipp Degen.
He scored just once in 18 appearances but has been far more effective at various levels for France.
The pacy forward has scored at every youth level for his country, including a brace against England Under-19s last season.
His exit from the Parc des Princes seemed inevitable from the moment he refused to sign a new contract with Paul le Guen's side as he entered the final year of his deal, and Liverpool soon stepped in with a bid thought to be around the Â£1.5million mark.