Vienna serves as the capital, most populous city, and one of the nine states of Austria. Situated on the eastern edge of the Vienna Woods and the northeasternmost foothills of the Alps, it marks the transition to the Pannonian Basin. The city lies on the Danube River, which is traversed by the highly regulated Wienfluss. It is completely surrounded by Lower Austria and positioned approximately 50 kilometers west of Slovakia and 60 kilometers south of Moravia in the Czech Republic.

The Romans founded a military camp called Vindobona at the site in the 1st century, which was elevated to a municipium with city rights in 212. After periods under Lombard, Avar, and Bavarian influence, Vienna became the seat of the Babenberg dynasty in 1155 and received formal city rights in 1221. The Habsburgs established it as the imperial seat in the 16th century, a role it maintained through the Austrian Empire's formation in 1804 until the dissolution of the Holy Roman Empire.

The city is broadly divided into inner districts numbered one to nine and outer districts ten to twenty-three, each functioning as decentralized administrative branches. Its historic centre features rich architectural ensembles, including Baroque palaces, gardens, and the late-19th-century Ringstrasse lined with grand buildings and monuments. The urban landscape reflects its imperial past, having been the residence of Habsburg emperors for centuries and hosting major political events like the Congress of Vienna in 1814–15.

Vienna is renowned for its rich musical heritage, having been home to celebrated composers such as Beethoven, Mozart, and Schubert. It played a pivotal role as a leading European music centre from the age of Viennese Classicism through the early 20th century. The city was also home to Sigmund Freud, the world's first psychoanalyst, and contributed significantly to modernism through movements like the Vienna Secession and the philosophy of Ludwig Wittgenstein.

Vienna has a population of 2,028,289 as of 2025, with its larger metropolitan area housing nearly 2.9 million people. It is the cultural, economic, and political centre of Austria and hosts major international organizations including the United Nations and OPEC. The city centre was designated a UNESCO World Heritage Site in 2001, though it was listed as endangered from July 2017 to July 2026 due to development pressures.