Marcel Duchamp 1887–1968, Blainville-Crevon, France) was a French artist who is often regarded as the key figure in the art of the 20th century, because he fundamentally changed how people thought about art.

He began as a somewhat conventional artist. This painting, ‘Chess game’, is from 1910.

In 1912 he became the sensation of New York with this painting, ‘Nude descending a staircase’, an abstraction of movement, which many considered an outrageous break with tradition.

In 1917 he submitted this upside-down urinal - titled ‘Fountain’ - to an art show, leading to further outrage and fame. In this gesture (an idea which has also been credited to Elsa von Freytag-Loringhoven), Duchamp suggested that whatever the artist says is art, thereby becomes art.

Here is another example of a work by Duchamp in which he makes small changes (or even no changes) to an existing object (a form he called a ‘Readymade’). This is from 1913 and is called ‘Bicycle wheel’.

Here is another, from 1914, called ‘Bottlerack’. 

What about this one, ‘50 cc of Paris Air’ (1919).

Marcel Duchamp made many more works, or gestures, or ideas… he paved the way for an explosion of creative directions including Pop Art, Performance Art and Conceptual Art.