Wilhelm Heinrich Otto Dix (German: [ˈvɪlhɛlm ˈhaɪnʁɪç ˈʔɔtoː ˈdɪks] ^ⓘ; 2 December 1891 – 25 July 1969) was a German painter and printmaker, noted for his ruthless and harshly realistic depictions of German society during the Weimar Republic and the brutality of war. Along with George Grosz and Max Beckmann, he is widely considered one of the most important artists of the Neue Sachlichkeit.

Otto Dix was born in Untermhaus, Germany, now a part of the city of Gera, Thuringia. The eldest son of Franz Dix, an iron foundry worker, and Louise, a seamstress who had written poetry in her youth, he was exposed to art from an early age. The hours he spent in the studio of his cousin, Fritz Amann, who was a painter, were decisive in forming young Otto's ambition to be an artist; he received additional encouragement from his primary school teacher. Between 1906 and 1910, he served an apprenticeship with painter Carl Senff, and began painting his first landscapes. In 1910, he entered the Kunstgewerbeschule in Dresden, now the Dresden Academy of Fine Arts, where Richard Guhr was among his teachers. At that time the school was not a school for the fine arts but rather an academy that concentrated on applied arts and crafts.

The majority of Dix's early works concentrated on landscapes and portraits which were done in a stylized realism that later shifted to expressionism.

When the First World War erupted, Dix volunteered for the German Army. He was assigned to a field artillery regiment in Dresden. In the autumn of 1915 he was assigned as a non-commissioned officer of a machine-gun unit on the Western front and took part in the Battle of the Somme. In November 1917, his unit was transferred to the Eastern front until the end of hostilities with Russia, and in February 1918 he was stationed in Flanders. Back on the western front, he fought in the German spring offensive. He earned the Iron Cross, 2nd class, and reached the rank of Vizefeldwebel. In August of that year he was wounded in the neck, and shortly after he took pilot training lessons.

He took part in an anti-aircraft course in Tongern, was promoted to Vizefeldwebel and after passing the medical tests transferred to Aviation Replacement Unit Schneidemühl in Posen. He was discharged from service on 22 December 1918 and was home for Christmas.

Dix was profoundly affected by the sights of the war, and later described a recurring nightmare in which he crawled through destroyed houses. He represented his traumatic experiences in many subsequent works, including a portfolio of fifty etchings called Der Krieg, published in 1924. Subsequently, he referred to the war again in The War Triptych, painted from 1929 to 1932.

At the end of 1918 Dix returned to Gera, but the next year he moved to Dresden, where he studied at the Hochschule für Bildende Künste. He became a founder of the Dresden Secession group in 1919, during a period when his work was passing through an expressionist phase. In 1920, he met George Grosz and, influenced by Dada, began incorporating collage elements into his works, some of which he exhibited in the first Dada Fair in Berlin. His early use of collage, in the context of the Weimar Republic, is evident in The Match Seller from 1920. Dix also participated in the German Expressionists exhibition in Darmstadt that year.

He met metalsmith Martha Koch in 1921, and they married in 1923. They had three children together. She was a frequent subject of his portraits.