Which country is the smallest euro-using state by area?

Vatican City is the smallest euro-using state by area.

Although Vatican City is not a member of the European Union, it uses the euro under a monetary agreement with the European Union through Italy. It is permitted to issue a limited number of euro coins bearing Vatican designs, which are legal tender throughout the euro area.

The Vatican replaced the lira with the euro in 2002. Its coins are especially popular with collectors because annual mintages are small and the designs often feature the pope or other symbols of the Holy See.

Monaco, San Marino and Andorra also use the euro without being EU members, but each has substantially more territory than Vatican City. The Holy See, which governs the Catholic Church, is legally distinct from Vatican City, the sovereign territorial state.