A stunning body of work

Maria LassnigSerpentine Gallery, London W2, until 8 June

Maria Lassnig is the discovery of the year - of the century. It would be hard to think of a greater artist of whom so little, at least in Britain, is known. Almost 90, Austrian, resident in Vienna after many decades in Paris and New York, Lassnig is as venerated in Continental Europe as Louise Bourgeois in the West, two warrior queens, yet we have never before had the opportunity to meet her tremendous paintings.

For that is what strikes from the start - the sense of a human encounter, the way Lassnig's pictures gesticulate, joke, expostulate, confide from the walls, sometimes in anguish or grief, acting upon you exactly like people. It is a sensation sharpened by the fact that people are precisely and solely what she paints: lone characters or, at the most, couples.

A man dangling from two rings gives you a sheepish smile, as if his discomfort was socially embarrassing. A woman tries to say something, mouth agape, from under the saucepan jammed on her head. Adam and Eve, fumbling in odd new long johns, appear absurdly paralysed by your presence. A naked woman points a gun at the viewer but another at herself, as if swithering between murder and self-defence. Madonna of the Pastries, a very fleshy nude, shoots you a challenging glance from an altar laid with exotic cakes, one of which looks suspiciously like a lifeless head. Eat or die? Live life to the full? Or is this a quizzical twist on the doctrine of transubstantiation?

Lassnig's pictures invite long looking, not least because they present you with such strange and bewildering propositions. One is always trying to fathom their human relationships, which turn out to be just as rivetingly impenetrable as those around us in real life; always trying to catch the pictures' charged but ambiguous tone.

Take The World Destroyer, in which a naked strongman tries to squeeze the world to death, as it seems, like Charles Atlas crushing a brick with his bare hands. In small-scale reproduction, the picture comes close to cartoon - a furious fatso struggling mightily with a silly little blow-up globe; that interpretation is available in the full-size reality too. But confronted by this figure in the Serpentine Gallery, his eyes frighteningly electric, his body summoned forcefully out of paint, and out of darkness, one senses a far more dreadful violence.

There is no index of scale, no reassuring hint of time or place. This dumb brutality is universal. Truly, the image comes at you like one of Goya's Black Paintings, a vision that goes beyond allegory, beyond words.

This is only possible because Lassnig is such a virtuoso painter. An award-winning draughtsman, she was the first woman to run a German-speaking school of art and her work is richly steeped in tradition. Hints of Titian and Rembrandt are conflated with what appear to be pastiches of the manly Modernists who were her contemporaries.

I'm sure I saw traces of Picasso in the ironically titled Dream Couple, two extruded biomorphs fit only for each other; in Bugbear, a bald bloke gets down on all fours to throttle what looks for all the world like a doll described in Matisse's distinctive arabesques. This man's obsession appears ludicrous, as demeaning as his pot-bellied pose. But what are we if not trapped in mind and body? Bent double, writhing, coupling hamfistedly, sometimes amputated or squirming like a Francis Bacon pope, Lassnig's figures are stuck inside their corpulent selves.

'Body-awareness' is how she describes her approach with wry understatement, for it would be hard to think of a living artist who paints more drastically exposed bodies with the exception of Lucian Freud. But Lassnig is the antidote to Freud's dead-end realism, constantly inventing new and prolific figurative forms with a life of their own.

These coinings run all the way from tragedy to high humour, often achieving a balancing feat between the two. A pair of violently jaunty figures swaggering across a seering citrus backdrop is nearly abstract, yet verging on caricature; all mouth, barb and shriek, they could be socialites out shopping but for the hint of cruel hood and blade. The future is bright, but bitter; this picture is called Children as Warriors

Lassnig is a great colourist and her colours seem to get younger as she grows older. What she amusingly calls her abstract scenarios - they're more pungently figurative than ever - take place against eye-popping yellows, reds and greens. There is something heraldic about these late works, old age's insights distilled into such clear and timeless emblems and yet they look the highest pitch of modernity.

It is remarkable how much force of personality floods out of Lassnig's art. Even if nobody had ever described her character, one could accurately deduce it from that of the paintings: strong, forthright, perennially alive and vulnerable to emotion, forever young, standing alone. It is no surprise that she has influenced more than one successive generation of painters.

But although Lassnig is a constantly ingenious self-portraitist - self with that saucepan, self defying dragon, self as a stuttering language machine - her work is not autobiography by other means. These vignettes that arrive out of a no-man's-land of pure whiteness or colour - no background, no context - multiply the misfortunes and emotions of one or two people into a commonwealth. They might originate with Lassnig, but they open out to include everyone else.

The most affecting work here, paradoxically, is the only one that hints at a specific place: the hospital we may all have to endure in the end. It is an unforgettable masterpiece, suffering and empathy irreducibly condensed in the geometry of the composition. A row of triangles - anglepoise lights - looms above a row of pillowed heads; the sharp shape is repeated over and again in noses, nightcaps and mouths as if the patients were institutionalised for good. Beneath, the bedding is drawn up in a horizontal line that divides both picture and patients: heads above the parapet, as it were; poor naked bodies below. What can keep body and soul together?

In Hospital, Lassnig makes visible what is felt but rarely shown, which could stand as her lifelong principle. She is being promoted by the Serpentine as a pioneer of the avant-garde and that is true too, but she is far more than that. Lassnig is a truth-revealing original.