Monaco is the smallest United Nations member state by total area.
The principality occupies only about 2 square kilometres on the French Riviera, making it smaller than every other UN member country. The only sovereign state with less territory is Vatican City, which is not a UN member state; it holds observer status instead. Monaco therefore takes the canonical answer when the question specifically limits the comparison to UN members.
Monaco is a sovereign city-state bordered on three sides by France and on the fourth by the Mediterranean Sea. Its compact territory is heavily urbanised, with famous districts such as Monte Carlo, Monaco-Ville, La Condamine and Fontvieille. Land reclamation has gradually expanded the principality, including the Le Portier district opened in 2024, but it remains far smaller than the next-smallest UN members.
Nauru, often mistaken for the answer because it is a tiny island republic, covers about 21 square kilometres. San Marino and Liechtenstein are also microstates, but both are much larger. Monaco joined the United Nations as a full voting member in 1993, which is the key detail separating it from Vatican City.