UEFA's executive committee, meeting at the association's headquarters at Nyon in the canton of Vaud, rubber-stamped the proposals, which were first made public last month, for the 2020 finals to be the first "Euro for Europe".
Previous tournaments have been held in one country or, as was the case at Euro 2012 in Poland and Ukraine, jointly-hosted by two neighbouring countries.
For 2020, UEFA have stipulated that there will be a maximum of one venue per country, and added that the two semi-finals and the final will all be held in the same stadium.
The remaining 12 winning bids will each host three group matches as well as one knockout tie from either the Round of 16 or the quarter-finals.
No nation will qualify automatically for the finals, but every host that qualifies will be guaranteed two home matches in the group phase.
No such guarantees would be given for the knockout stages.
UEFA also said they will try to take travel distances into account when allocating hosting teams to groups, "for example, and if feasible, with flights not exceeding two hours' duration between two host cities to allow easy access to travelling fans."
UEFA president Michel Platini insisted everything would be done to make a pan-European event — to coincide with the 60th anniversary of the first European Nations Cup — as fan-friendly as possible.
"We will play across the whole of Europe. All 53 national federations can be candidates," he said.