A sprightly old woman wearing a loud print dress and bedroom slippers sat on an armchair in the main room, watching the art critics with an amused eye, holding court as, one by one, they stopped to pay homage. Dina Vierny didn't have to travel far for the opening of the Maillol Peintre exhibition this summer - just a few floors down from her rooftop apartment above the museum she created. She needs to be near the splendid records of her youth: "I wake up at night to go and see them," she says of the paintings and sculptures she posed for 60 years ago.

The years have made Vierny short and plump, but the dark eyes still sparkle. The long plait down her back has thinned, and Ms Vierny dyes it black now. Forgive my indiscretion, I asked, but how old are you? "It's not indiscreet!" she hooted, her laughter breaking the church-like silence of the museum. "I am part of the history of art!" she declared, adding that she is proud to be 82 years old, still organising exhibitions of her hero's work in London, Valence and Sπo Paolo.

Aristide Maillol met Dina Vierny in 1934, when he was 73 and she a 15-year-old lycΘe student. She was in awe of him, because after Rodin died in 1918, Maillol was considered the greatest living French sculptor. Struck by Vierny's resemblance to Maillol's heavy-limbed, majestic stone and bronze nudes, the architect of the MusΘe d'Art Moderne suggested that the ageing artist, who was going though a severe depression, contact the young model. "Mademoiselle," Maillol wrote to her.

"I am told you resemble a Maillol and a Renoir - I would be satisfied with a Renoir." Dina Vierny visited Maillol's studio at Marly. "I meant to stay a few hours; I stayed 10 years," she says. The sight of one of his sculptures made flesh shook Maillol out of his lethargy. Inspired by Vierny, he not only began sculpting again, but returned to his first love, painting.

Born to a family of poor wine-growers in the Mediterranean port of Banyuls in 1861, Aristide Maillol wanted to be a painter from the age of 13. An artistic son was a catastrophe in his milieu, but when the phylloxera epidemic destroyed the family's vineyards, Maillol's Aunt Lucie relented and sent the young Aristide to art school in Perpignan. After three failed applications, Maillol was finally accepted by the ╔cole des Beaux-Arts in Paris.

Maillol was thrilled by the work of the post-impressionists he saw at the Salon des IndΘpendants. His early paintings are an odd combination of styles: outright copies of Puvis de Chavannes, haystacks that could have been painted by van Gogh, his Aunt Lucie looking just like Whistler's mother, colours and models that seem borrowed from Matisse, Monet and Renoir - with a few Botticelli faces and quattrocento portraits in profile.

But the most powerful influence was that of Paul Gauguin, whom Maillol met during the 1889 World's Fair. "Gauguin's painting was a revelation for me," Maillol said. "Beaux-Arts blindfolded me instead of enlightening me." Maillol's palette is lighter, but he adopted Gauguin's use of flat surfaces and foliage for decoration. Like Gauguin, he abandoned perspective and was attracted to symbolism and japonisme.

Maillol's first two successful paintings, the luminous House In Roussillon (1888) and Portrait Of Mademoiselle Jeanne Faraill (1889) showed great talent. His first art teacher's daughter is a serious little girl in a red and white striped dress and black stockings, standing on an oriental carpet. She is part doll, part adult. "I love the rose-like freshness of very young girls," Maillol told his biographer Judith Cladel. "The look in their eyes shows faith in life, confidence untouched by sadness. The young girl is for me the wonder of the world and a perpetual joy."

Maillol idealised and adored women. In this first exhibition devoted solely to his paintings, the only males are a self-portrait, the painter's infant son, Lucien, and two figures copied from Puvis de Chavannes. Otherwise, Maillol's world is inhabited solely by women. Woman With A Parasol (1892), on loan from the MusΘe d'Orsay, is his best-known painting. A graceful figure in a pink wallpaper dress with fluttering ribbons raises her gloved hand to the brim of a straw hat, against horizontal swathes of sky, sea and sand.

With Gauguin's encouragement, Maillol set up a tapestry workshop in Banyuls in 1894. He fell in love with and married Clotilde Narcisse, whom he'd hired to make tapestries. In an 1894 portrait, the bride posed in a simple black dress with her hair pulled up. Large almond eyes look seductively from an angular face with an exquisite mouth.

Marriage brought the first awakening in Maillol's work. With no need to pay for nude models, he abandoned the frou-frou hats and dresses of his earlier work and joyously took up the theme that would fascinate him for the rest of his life - the female body - usually in the open air, often walking in water. He and Clotilde wandered the foothills of the eastern Pyrenees. "I lived my most beautiful hours there," Maillol recalled later. "The entire mountain range saw my wife naked. She was beautiful." Quoted by Dina Vierny in a book on Maillol, he was grateful to Clotilde. "She posed in the cold. At a time of great poverty, she was hungry with me, without complaining; I cannot forget that." The nude led Maillol to sculpture, and by 1900 he all but stopped painting. For three and a half decades he was famed as a sculptor. Indeed, Maillol considered himself an inferior painter - one reason his canvases were not exhibited earlier.

It took the shock of meeting Dina Vierny for the old man to take up brushes again - and invent a sculptural style of painting that was all his own. Vierny was studying chemistry and physics at lycΘe, and Maillol affectionately called her his "laboratory rat". Sessions were different, depending on whether he was painting or sculpting, Vierny says. "During the sculptures, I could move a little. For a sculpture, he always started with one foot.

It was extraordinary seeing the form take shape." Most artists' models were uneducated girls, Vierny says. But she and Maillol discussed poetry. "He told his painter friend Maurice Denis: 'She is young, she is beautiful and she speaks like Gide'," Vierny recalls proudly. Maillol was so pleased that he suggested Vierny also pose for his friends Matisse, Bonnard and Dufy.

The nude paintings of Dina Vierny, all from the last decade of Maillol's life, are so suffused with sensuality that it is difficult to believe the painter and model were not lovers, despite the 58-year difference in ages. But when I dared ask, Claude Unger, the press attachΘe for the museum, quickly corrected me. "Madame Maillol was extremely jealous," she said. "It was never a love relationship. When Mme Maillol died in the 1950s, she told her son to make Dina the executor - if there had been anything between them, she wouldn't have dreamed of it."

During the second World War, Dina Vierny joined the Resistance. The red dress she wore was a signal to refugees from the Nazis, whom she helped to reach Spain.

Maillol let her use his little farm outside Banyuls as a meeting place, and showed the rΘsistants the fastest escape path through the mountains, which became known as the "route Maillol".

Aristide Maillol was killed in a car crash in 1944, on his way to visit his painter friend, Raoul Dufy.

Among his last works were several paintings of Dina in the red dress of resistance, and a tribute to Gauguin in which Dina stands in a wheatfield, tying her scarf - like one of Gauguin's Tahitian models.

Maillol's last sculpture, Harmony, stands out from others in that is not meant to be a stylised, generic nude woman, but a likeness of his muse, Dina.

Maillol Peintre is at the Fondation Dina Vierny-MusΘe Maillol, 61 Rue de Grenelle, 75007 Paris, until October 20th. Open every day except Tuesday, 11 a.m.-6 p.m.