The influence of the new Vitra Design Museum will be great, perhaps as great as the high-tech Pompidou Centre of 1977 by Renzo Piano and Richard Rogers, or the postmodern Stuttgart Staatsgalerie of James Stirling in 1984. It is the first European work of the Californian architect Frank Gehry, a man whose distinctly unconventional ways with buildings have until now been a well-kept secret outside his home state. Now he is introducing a new aesthetic that thankfully has nothing whatever to do with the classical-versus-modem architectural debate in Britain. It stands outside all that.

Gehry's museum - a museum of chairs - opened on Friday in the town of Weil am Rhein, just outside Basle and just in Germany, in that comer of Europe where people habitually speak at least three languages and national borders seem to be meaningless. Here, amid orchards and vineyards, he has created an extraordinary collage of a building. Outside, its jumble of forms suggest almost any imagery you care to apply - a church, a ship, a swan. Inside, it is simply one of the best new galleries anywhere, a masterly sequence of spaces that are each utterly different, each beautifully and naturally lit, and each visually linked most ingeniously with the others.

If there is any precedent for this kind of architecture, it is in early Expressionist films such as The Cabinet of Dr Caligari, in which the set is deliberately distorted for dramatic effect. The Vitra museum takes ordinary elements - ramps, stairs, a corner with a window, a lift tower - pulls them apart and re-assembles them to challenge our notions of what a building should be. Outside of film or stage design, it has more to do with sculpture than architecture, is closer perhaps to the work of Richard Serra, Anthony Caro or Paul Neagu. But Gehry insists he is an architect: sculptors, he says, do not have to design things such as toilets. At the same time, he concedes that there is no clear dividing line between what he does and what artists do.

What is this powerful building doing here? It exists simply because of the patronage of an enlightened manufacturer of office furniture, Rolf Fehlbaum of Vitra International. Fehlbaum believes in unconventional and controversial design, and has amassed a unique collection of European and American chairs, many designed by internationally famous architects, made between 1850 and the present day. Wanting to expand his factory in Weil, he decided to commission a museum for the chairs as part of the same contract. Enter Gehry.

Fehlbaum is singlemindedly making Weil am Rhein into a design mecca. His only equivalent in the UK might be Sir Terence Conran, whose Conran Foundation finances London's Design Museum. But commerce and culture are far closer together in Fehlbaum's vision. The Gehry commission, and his growing patronage of avant-garde architects and designers for new chairs, is merely the latest manifestation of his beliefs. He has the habit, unusual in a manufacturer, of hiring some of the world's more interesting architects to design buildings for him.

He started in 1981 with a factory and office building by the British modernist Nick Grimshaw in his then-characteristic "crinkly tin shed" aesthetic. More recently he employed Eva Jiricna from London to spruce up a 1950s administration building and place an exuberant canopy in front. Then came Gehry. Fehlbaum asked him to do another factory building, plus the museum alongside, as part of the same package. The factory is plain white and rectangular, scarcely differing from Grimshaw's contribution in form. On the side facing the museum, however, it sprouts Gehry's signature serpentine growths, its rigid grid suddenly subverted as if by the biological influence of the museum.

Inevitably a word has been coined to describe this kind of architecture. It is, we are told, "deconstructivism". Gehry, however, is not so easily pigeonholed. For one thing, he's been around too long: now 60, he was designing houses this way long before the term was invented. In California, his strange buildings could be dismissed as just another manifestation of the weird West Coast world-view. Away from this in Europe, it's suddenly clear how very good he is.

He once explained his style as a simple matter of designing a room at a time, rather than a building as a whole. He admires both the romanesque churches of southern France, and the sinuous forms of fish and snakes. The Vitra museum certainly has a basilica-like quality, something reinforced by the central cruciform rootlight. In its rejection of conventional styles it even recalls aspects of Le Corbusier's revolutionary 1950 chapel at Ronchamp, not a million miles away.

Fehlbaum's mission does not stop here. He has signed up Zaha Hadid, a British-based architect whose own splintered, fragmented, deconstructivist style makes Gehry seem almost mainstream. She is to do a fire station for the factory complex. And on the back seat of Fehlbaum's car is a model of a conference building by yet another noted architect, the Japanese minimalist Tadao Ando.

Why does he bother? "You could call it self-sponsorship," says Fehlbaum. "I'd rather do this than spend money sponsoring some local opera company. And it is making us famous."

You can bet that aspects of this remarkable new museum will rapidly find their way into the international architectural vocabulary: architects absorb strong new ideas almost as quickly as fashion designers. Meanwhile, Gehry should be invited to build in Britain, and soon. Something as startling as this might broaden the architectural debate a little.