Warsaw (Polish: Warszawa, [varˈʂava] (listen)), officially the Capital City of Warsaw, is the capital and largest city of Poland. The metropolis stands on the River Vistula in east-central Poland, and its population is officially estimated at 1.86 million residents within a greater metropolitan area of 3.1 million residents, which makes Warsaw the 6th most-populous city in the European Union. The city area measures 517 km² (200 sq mi) and comprises 18 districts, while the metropolitan area covers 6,100 km² (2,355 sq mi). Warsaw is an alpha global city, a major cultural, political and economic hub, and the country's seat of government.

Warsaw traces its origins to a small fishing town in Masovia. The city rose to prominence in the late 16th century, when Sigismund III decided to move the Polish capital and his royal court from Kraków. Warsaw served as the de facto capital of the Polish–Lithuanian Commonwealth until 1795, and subsequently as the seat of Napoleon's Duchy of Warsaw. The 19th century and its Industrial Revolution brought a demographic boom which made it one of the largest and most densely populated cities in Europe. Known then for its elegant architecture and boulevards, Warsaw was bombed and besieged at the start of World War II in 1939. Much of the historic city was destroyed and its diverse population decimated by the Ghetto Uprising in 1943, the general Warsaw Uprising in 1944 and systematic razing.

Warsaw is served by two international airports, the busiest being Warsaw Chopin and the smaller Warsaw Modlin intended for low-cost carriers. Major public transport services operating in the city include the Warsaw Metro, buses, commuter rail service and an extensive tram network. The city is a significant centre of research and development, business process outsourcing, and information technology outsourcing. The Warsaw Stock Exchange is the largest and most important in Central and Eastern Europe. Frontex, the European Union agency for external border security, and ODIHR, one of the principal institutions of the Organization for Security and Co-operation in Europe, have their headquarters in Warsaw. As of 2022, Warsaw has one of the highest number of skyscrapers in Europe while Varso Place is the tallest building in the European Union.

The city is home to renowned universities such as the University of Warsaw, the Warsaw University of Technology, SGH Warsaw School of Economics, Chopin University of Music and Kozminski University. It also hosts the Polish Academy of Sciences, National Philharmonic Orchestra, the National Museum, Zachęta Art Gallery and the Warsaw Grand Theatre, the largest of its kind in the world. The reconstructed Old Town, which represents examples of nearly every European architectural style and historical period, was listed as a World Heritage Site in 1980. Other architectural attractions include the Royal Castle, Sigismund's Column, the Wilanów Palace, the Palace on the Isle, St. John's Archcathedral, Main Market Square, and numerous churches and mansions along the Royal Route. The Warsaw Zoo is among the largest and most-visited zoological gardens in the country. The city possesses thriving arts and club scenes, gourmet restaurants and large urban green spaces, with around a quarter of the city's area occupied by parks. In sports, the city is known as the home of the top-tier football club Legia Warsaw, the Warsaw Marathon and Poland's national football stadium Stadion Narodowy.