Paul César Helleu (17 December 1859 – 23 March 1927) was a French oil painter, pastel artist, drypoint etcher, and designer, best known for his numerous portraits of beautiful society women of the Belle Époque. He also conceived the ceiling mural of night sky constellations for Grand Central Terminal in New York City. He was also the father of Jean Helleu and the grandfather of Jacques Helleu, both artistic directors for Parfums Chanel.


Paul César Helleu was born in Vannes, Brittany, France. His father, who was a customs inspector, died when Helleu was in his teens. Despite opposition from his widowed mother, he then went to Paris and studied at Lycée Chaptal. In 1876, at age 16, he was admitted to the École des Beaux-Arts, beginning academic training in art with Jean-Léon Gérôme. Helleu attended the Second Impressionist Exhibition in the same year, and made his first acquaintances with John Singer Sargent, James McNeill Whistler, and Claude Monet. He was struck by their modern, bold alla prima technique and outdoor scenes, so far removed from the studio. To survive following graduation, Helleu took a job with the firm Théodore Deck Ceramique Française hand-painting fine decorative plates. At this same time, he met Giovanni Boldini, a portrait painter with a facile, bravura style, who became a mentor and comrade, and strongly influenced his future artistic style.
When he was 18 years old, Helleu established a close friendship with John Singer Sargent, four years his senior, that was to last his lifetime. Already becoming established, Sargent was receiving commissions for his work. Helleu had not sold anything, and was deeply discouraged almost to the point of abandoning his studies. When Sargent heard this, he went to Helleu and picked one of his paintings, praising his technique. Flattered that Sargent would praise his work, he offered to give it to him. Sargent replied, "I shall gladly accept this, Helleu, but not as a gift. I sell my own pictures, and I know what they cost me by the time they are out of my hand. I should never enjoy this pastel if I hadn't paid you a fair and honest price for it." With this he paid him a thousand-franc note.