Les XX was in some ways a successor to the group L'Essor. The rejection of 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.
In 1893, the society of Les XX was transformed into "La Libre Esthétique".
- History 1
- Eleven founding members 2
- Nine invited members 3
- Twelve later invited members 4
The ten Annual Exhibitions of Les XX, 1884–1893 5
- 1884 5.1
- 1885 5.2
- 1886 5.3
- 1887 5.4
- 1888 5.5
- 1889 5.6
- 1890 5.7
- 1891 5.8
- 1892 5.9
- 1893 5.10
- Notes 6
Further reading 7
- Primary sources 7.1
- Secondary sources 7.2
- External links 8
Les XX was founded on 28 October 1883 in Brussels and held annual shows there between 1884 and 1893, usually in January–March. The group was founded by 11 artists who were unhappy with the conservative policies of both the official academic Salon and the internal bureaucracy of
The first concert was centered on work by César Franck and the first performance of Ernest Chausson's Poème de l'amour et la mer The second concert contained works by d'Indy, Castillon, Fauré, Chabrier and Bréville. The third and final concert featured the première of Guillaume Lekeu's Violin Sonata, with also performances of compositions by Charles Smulders, Paul Gilson, Dorsan van Reysschoot and Alexis de Castillon.
Paul Verlaine discussed the contemporary poetry.
Three concert evenings were organised. The first concert presented the first version of Paul Gilson's La Mer, Guillaume Lekeu's Andromède and music by Nikolai Rimsky-Korsakov, Alexander Glazunov, and Franz Servais. The second showcased music by Alexis de Castillon, César Franck, Charles Bordes, Louis de Serres and Emmanuel Chabrier. The final concert included the first performance of Vincent d'Indy's Suite in D and Ernest Chausson's Concert. The other music played was composed by Gabriel Fauré, Charles Bordes, Camille Chevillard and Albéric Magnard.
 Retrospective of
Memorial concert for César Franck and a second concert with new work by Vincent d'Indy, and work by other followers of Franck, including Bordes, Duparc, Bréville, Chausson, Tiersot, Vidal,and Camille Benoît. Also played was work by Fauré and Emmanuel Chabrier. A third concert focused on Russian composers, with works by Pyotr Ilyich Tchaikovsky, Alexander Borodin, Nikolai Shcherbachov, Nikolai Rimsky-Korsakov and Alexander Kopylov.
 First exhibitions of decorative art, including posters and book illustrations by
Three concerts were given, with the first centered on Belgian composers like Auguste Dupont, Léon Soubre, Joseph Jacob, Paul Gilson and Gustave Huberti. The second and third concert focused on the French composers, with works by Fauré, Franck, d'Indy, and Castillon in the second concert. Vincent d'Indy performed his Symphonie Cévenole in the third concert. Other composers whose work was performed were Fauré, Franck, Bréville, Bordes, Chausson, Albéric Magnard and Paul Vidal.
Exhibits by invited artists including Odilon Redon, Paul Cézanne, Paul Signac, Henri de Toulouse-Lautrec, Alfred Sisley, Paul Gauguin and Vincent van Gogh. Durint the 1890 expo was sold the only painting Vincent van Gogh sold during his lifetime.
At the first concert, the music was composed by César Franck, Pierre de Bréville, Ernest Chausson, Gabriel Fauré and Julien Tiersot. The music was played in part by the Quatuor Ysaÿe, as happened in the next few years. The second concert was centered on Gabriel Fauré, with additional music by d'Indy, Charles Bordes and Henri Duparc.
.Vision After the Sermon Included is Gauguin's masterpiece 
Auguste Villiers de l'Isle-Adam was one of the invited writers.
First performance of Vincent d'Indy's Poème des Montagnes.
.A Sunday Afternoon on the Island of La Grande Jatte The major work shown is Seurat's 
First performance of César Franck's Violon Sonata.
The first of ten annual exhibitions was held on 2 February at the Palais des Beaux-Arts in Brussels.
The ten Annual Exhibitions of Les XX, 1884–1893
- Felicien Rops 1833–1898
- George Minne 1866–1941
- Anna Boch 1848–1926 (member 1885–1893: only female member)
- Henry van de Velde (member starting 1888)
- Guillaume Charlier
- Henry De Groux
- Robert Picard (artist) b. 1870
- Jan Toorop (Dutch)
- Odilon Redon (French)
- Paul Signac (French)
- Isidore Verheyden (member 1884–1888)
Twelve later invited members
- Guillaume Vogels
- Achille Chainaye 1862–1915
- Jean Delvin 1853–1922
- Jef Lambeaux
- Périclès Pantazis (Greek) 1849–1884
- Frans Simons 1855–1919
- Gustave Vanaise 1854–1902
- Piet Verhaert 1852–1908
- Théodore Verstraete 1850–1907
Nine invited members
- James Ensor 1860–1949 (member until 1893)
- Théo van Rysselberghe 1862–1926 (member until 1893)
- Fernand Khnopff 1858–1921 (member until 1893)
- Alfred William Finch
- Frantz Charlet 1862–1928 
- Paul Du Bois
- Charles Goethals c. 1853–85
- Darío de Regoyos (Spanish)
- Willy Schlobach 1864–1951
- Guillaume Van Strydonck 1861–1937
- Rodolphe Wytsman 1860–1927
Eleven founding members
Together with Maus, the influential jurist Edmond Picard and the Belgian poet Emile Verhaeren provided the driving force behind an associated periodical, L'Art Moderne, which was started in 1881. This publication aggressively defended Les XX from attacks by critics and members of the visiting public. Picard polemically fomented tensions both with the artistic establishment and within Les XX. By 1887, six of the more conservative original members had left, sometimes under pressure from Picard and Maus, to be replaced by artists who were more sympathetic to the cause. Altogether, Les XX had 32 members during the ten years of its existence.
There was a close tie between art, music and literature among the Les XX artists. During the exhibitions, there were literary lectures and discussions, and performances of new classical music, which from 1888 were organised by Vincent d'Indy, with from 1889 until the end in 1893 very frequent performances by the Quatuor Ysaÿe. Concerts included recently composed music by Claude Debussy, Ernest Chausson and Gabriel Fauré. Leading exponents of the Symbolist movement who gave lectures include Stéphane Mallarmé, Théodore de Wyzewa and Paul Verlaine.