Melbourne ( (listen) MEL-bərn; Boonwurrung/Woiwurrung: Narrm or Naarm) is the capital and most populous city of the Australian state of Victoria, and the second-most populous city in both Australia and Oceania. Its name generally refers to a 9,993 km² (3,858 sq mi) metropolitan area known as Greater Melbourne, comprising an urban agglomeration of 31 local municipalities, although the name is also used specifically for the local municipality of City of Melbourne based around its central business area. The metropolis occupies much of the northern and eastern coastlines of Port Phillip Bay and spreads into the Mornington Peninsula, part of West Gippsland, as well as the hinterlands towards the Yarra Valley, the Dandenong and Macedon Ranges. It has a population of almost 5 million (19% of the population of Australia, as per 2021 census), mostly residing to the east side of the city centre, and its inhabitants are commonly referred to as "Melburnians".

The area of Melbourne has been home to Aboriginal Victorians for over 40,000 years and serves as an important meeting place for local Kulin nation clans. Of the five peoples of the Kulin nation, the traditional custodians of the land encompassing Melbourne are the Boonwurrung, Wathaurong and the Wurundjeri peoples. A short-lived penal settlement was built at Port Phillip, then part of the British colony of New South Wales, in 1803, but it was not until 1835, with the arrival of free settlers from Van Diemen's Land (modern-day Tasmania), that Melbourne was founded. It was incorporated as a Crown settlement in 1837, and named after the then British Prime Minister, William Lamb, 2nd Viscount Melbourne. In 1851, four years after Queen Victoria declared it a city, Melbourne became the capital of the new colony of Victoria. During the 1850s Victorian gold rush, the city entered a lengthy boom period that, by the late 1880s, had transformed it into one of the world's largest and wealthiest metropolises. After the federation of Australia in 1901, it served as the interim seat of government of the new nation until Canberra became the permanent capital in 1927. Today, it is a leading financial centre in the Asia-Pacific region and ranks 32nd globally in the March 2022 Global Financial Centres Index.

Melbourne is home to many of Australia's best-known landmarks, such as the Melbourne Cricket Ground, the National Gallery of Victoria and the World Heritage-listed Royal Exhibition Building. Noted for its cultural heritage, the city gave rise to Australian rules football, Australian impressionism and Australian cinema, and has more recently been recognised as a UNESCO City of Literature and a global centre for street art, live music and theatre. It hosts major annual international events, such as the Australian Grand Prix and the Australian Open, and also hosted the 1956 Summer Olympics. Melbourne consistently ranked as the world's most liveable city for much of the 2010s.

Melbourne Airport, also known as the Tullamarine Airport, is the second-busiest airport in Australia, and the Port of Melbourne is the nation's busiest seaport. Its main metropolitan rail terminus is Flinders Street station and its main regional rail and road coach terminus is Southern Cross station. It also has Australia's most extensive freeway network and the largest urban tram network in the world.