Les XX (French; "Les Vingt"; French pronunciation: [le vɛ̃t]; lit. 'The 20') was a group of twenty Belgian painters, designers and sculptors, formed in 1883 by the Brussels lawyer, publisher, and entrepreneur Octave Maus. For ten years, they held an annual exhibition of their art; each year 20 other international artists were also invited to participate in their exhibition. Painters invited include Camille Pissarro (1887, 1889, 1891), Claude Monet (1886, 1889), Georges Seurat (1887, 1889, 1891, 1892), Paul Gauguin (1889, 1891), Paul Cézanne (1890), and Vincent van Gogh (1890, 1891 retrospective).
Les XX was in some ways a successor to another group, L'Essor. The rejection of James Ensor's The Oyster Eater in 1883 by L'Essor Salon, following the earlier rejection by the Antwerp Salon, was one of the events that led to the formation of Les XX. The ideal of the group responded to the theories of Viollet le Duc, in particular that of the integration of the so-called minor arts (decorative arts) with the major arts (architecture).
In 1893, the society of Les XX was transformed into "La Libre Esthétique".