The sovereignty of which city was established by 1929's Lateran Treaty?

The 1929 Lateran Treaty established the sovereignty of Vatican City.

The treaty was one part of the Lateran Pacts, signed on February 11, 1929, by the Kingdom of Italy and the Holy See. It settled the long-running “Roman Question,” the dispute created when Italian unification absorbed the Papal States in the 19th century. The agreement recognized Vatican City as an independent state under the sovereignty of the Holy See.

The treaty became effective on June 7, 1929. Vatican City provided the papacy with a small but independent territorial base, ensuring that the Holy See could conduct international affairs without being legally subject to Italy. Italy also recognized the special position of the Catholic Church and provided financial compensation connected with the loss of the Papal States.

The Holy See and Vatican City are related but not identical. Vatican City is the sovereign territory; the Holy See is the central governing authority of the Catholic Church and the entity that maintains diplomatic relations. The Lateran Pacts were revised in 1984, but Vatican City's sovereignty continues.