There were SEVERAL treaties of Vienna:

Treaty of Vienna (1606) (HRE/Hungary - freedom of religion)

Treaty of Vienna (1656) Austro-Polish alliance in the Second Northern War, ineffective

Treaty of Vienna (1657) Austro-Polish alliance in the Second Northern War, effective

Treaty of Vienna (1725) Austria/Spain

Treaty of Vienna (1731) Britain/Austria - alliance

Treaty of Vienna (1738) (or The Peace of Vienna) Multiple parties - resolved war of Polish succession

Treaty of Vienna (1809) (ALSO known as the Treaty of Schönbrunn) France/Austria - following Austria's defeat during the Napoleonic Wars

Treaty of Vienna (1815) can refer to several DIFFERENT treaties notably

Treaty of Vienna of 25 March 1815, (also known as "Treaty of General Alliance") when Austria, Britain, Prussia and Russia agreed to put 150,000 men in the field against Napoleon Bonaparte.(see wikisource:DECLARATION at the Congress of Vienna).

Treaty of Vienna of 9 June 1815, (also known as the "Final Act of the Congress of Vienna"), embodying all the separate treaties agreed at the Congress by the European powers.

Treaty of Vienna (1864) Austria/Prussia/Denmark - concluded the Second Schleswig War

Treaty of Vienna (1866) Austria/France/Italy

Treaty of Vienna (1878), Austria/Prussia/Denmark

Treaty of Vienna (1955), re-established the state of Austria after the Second World War

Joint Comprehensive Plan of Action, the final agreement on the 2015 Iran nuclear deal framework, signed in Vienna