The Guggenheim Museum Bilbao is a museum of modern and contemporary art, designed by Canadian-American architect Frank Gehry, and located in Bilbao, Basque Country, Spain. The museum was inaugurated on 18 October 1997 by King Juan Carlos I of Spain.

It is built alongside the Nervion River, which runs through the city of Bilbao to the Cantabrian Sea. The Guggenheim is one of several museums belonging to the Solomon R. Guggenheim Foundation. The museum features permanent and visiting exhibits of works by Spanish and international artists.

One of the most admired works of contemporary architecture, the building has been hailed as a "signal moment in the architectural culture", because it represents "one of those rare moments when critics, academics, and the general public were all completely united about something." The museum was the building most frequently named as one of the most important works completed since 1980 in the 2010 World Architecture Survey among architecture experts. The Solomon R. Guggenheim Foundation selected Frank Gehry as the architect, and its director, Thomas Krens, encouraged him to design something daring and innovative. The curves on the exterior of the building were intended to appear random; the architect said that "the randomness of the curves are designed to catch the light". The interior "is designed around a large, light-filled atrium with views of Bilbao's estuary and the surrounding hills of the Basque country." The atrium, which Gehry nicknamed The Flower because of its shape, serves as the organizing center of the museum.

When the Guggenheim Museum Bilbao opened to the public in 1997, it was immediately hailed as one of the world's most spectacular buildings in the style of Deconstructivism (although Gehry does not associate himself with that architectural movement), a masterpiece of the 20th century. Architect Philip Johnson described it as "the greatest building of our time", while critic Calvin Tomkins, in The New Yorker, characterized it as "a fantastic dream ship of undulating form in a cloak of titanium," its brilliantly reflective panels also reminiscent of fish scales. Herbert Muschamp praised its "mercurial brilliance" in The New York Times Magazine. The Independent calls the museum "an astonishing architectural feat". The building inspired other structures of similar design across the globe, such as the Cerritos Millennium Library in Cerritos, California.

The museum is seamlessly integrated into the urban context, unfolding its interconnecting shapes of stone, glass and titanium on a 32,500-square-meter site along the Nervión River in the old industrial heart of the city; while modest from street level, it is most impressive when viewed from the river. With a total 256,000 square feet, it had more exhibition space than the three Guggenheim collections in New York and Venice combined at that time. Eleven thousand square meters of exhibition space are distributed over nineteen galleries, ten of which follow a classic orthogonal plan that can be identified from the exterior by their stone finishes. The remaining nine galleries are irregularly shaped and can be identified from the outside by their swirling organic forms and titanium cladding. The largest gallery, measures 30 meters wide and 130 meters long. In 2005, it housed Richard Serra's monumental installation The Matter of Time, which Robert Hughes dubbed "courageous and sublime".

The building was constructed on time and budget, which is rare for architecture of this type. In an interview in Harvard Design Magazine, Gehry explained how he did it. First, he ensured that what he calls the "organization of the artist" prevailed during construction, to prevent political and business interests from interfering with the design. Second, he made sure he had a detailed and realistic cost estimate before proceeding. Third, he used computer visualizations produced by his own Digital Project software and collaborated closely with the individual building trades to control costs during construction.

The museum notably houses "large-scale, site-specific works and installations by contemporary artists, such as Richard Serra's 340 ft-long Snake, and displays the work of Basque artists, "as well as housing a selection of works" from the Foundation's modern art collection. In 1997, the museum opened with "The Guggenheim Museums and the Art of This Century", a 300-piece overview of 20th-century art from Cubism to new media art. Most pieces came from the Guggenheim's permanent collection, but the museum also acquired paintings by Willem de Kooning, Mark Rothko and Clyfford Still and commissioned new works by Francesco Clemente, Anselm Kiefer, Jenny Holzer and Richard Serra.

The exhibitions change often; the museum generally hosts thematic exhibitions, centered for example on Chinese or Russian art. Traditional paintings and sculptures are a minority compared to installations and electronic forms. The highlight of the collection, and its only permanent exhibit, is The Matter of Time (incorporating an earlier work, Snake), a series of weathering steel sculptures designed by Serra, which is housed in the 430-foot (130 m) Arcelor Gallery (formerly known as the Fish Gallery but renamed in 2005 for the steel manufacturer that sponsored the project). The collections usually highlight Avant-garde art, 20th century abstraction, and non-objective art. When the museum announced the 2011 exhibition "The Luminous Interval", a show of artwork belonging to Greek businessman Dimitris Daskalopoulos, who is also a museum trustee, this met with criticism of, among other things, too much curatorial power for a serious benefactor. In 2012 David Hockney's exhibition drew over 290,000 visitors to the museum.

The museum was opened as part of a revitalization effort for the city of Bilbao. Almost immediately after its opening, the Guggenheim Bilbao became a popular tourist attraction, drawing visitors from around the globe. In its first three years, almost 4 million tourists visited the museum, helping to generate about €500 million in economic activity. The regional council estimated that the money visitors spent on hotels, restaurants, shops and transport allowed it to collect €100 million in taxes, which more than paid for the building cost. The so-called "Bilbao effect" refers to how the museum transformed the city. The term, however, has also been employed by critics who have denounced the museum as a symbol of gentrification and cultural imperialism. The Wall Street Journal suggested that the Bilbao effect should be called the Bilbao anomaly, "for the iconic chemistry between the design of building, its image and the public turns out to be rather rare."

The building has been featured in such media references as the opening scene of the 1999 James Bond film The World Is Not Enough, or the 2007 film Sivaji: The Boss, in which it is the setting for the song Style, composed by A.R. Rahman. Mariah Carey's music video "Sweetheart", directed by Hype Williams, shows singers Dupri and Carey in various locations at the Guggenheim Museum Bilbao. The building is also featured in the computer game SimCity 4 as a buildable landmark.

Bilbao: The Fascinating Transformation (video)