It will be France.
The other two candidates were Turkey (which lost the final vote in a nail-biter, 7-6) and Italy. Some will view this as unfair as France and Italy have each hosted the Euros twice (as well as the World Cup) while Turkey has never hosted a major tournament. (Conspiracy theorists will note that the UEFA President, Michel Platini, is French as well - though he did not have a vote.) But honestly it's the most sensible choice. Turkey is poor, has some issues with fan security, and would need massive upgrades to its infrastructure and stadiums. It's anyone's guess if they could pull that off. The 2012 Euro host countries (Poland and Ukraine) are experiencing their own problems in this area, which probably made voters gunshy about giving it to a country that is still poorer and more inaccessible. As for Italy, most of its stadiums are in poor condition; the main argument for giving Italy the competition was that it would spur the Italians to get going on construction that should have been done earlier. France is the safest choice of the three. It doesn't have nearly as much construction to do and has a lot of experience in hosting major events.