Ludwig Mies van der Rohe (/miːs ... roʊ/ MEESS-...-ROH; German: [ˈluːtvɪç ˈmiːs fan deːɐ̯ ˈʁoːə]; born Maria Ludwig Michael Mies; March 27, 1886 – August 17, 1969) was a German and American architect, academic, and interior designer. He was commonly referred to as Mies, his surname. He is regarded as one of the pioneers of modern architecture.

In the 1930s, Mies was the last director of the Bauhaus, a ground-breaking school of modernist art, design and architecture in Germany. After Nazism's rise to power, due to its strong opposition to modernism, he emigrated to the United States in 1937 or 1938. He accepted the position to head the architecture school at what is today the Illinois Institute of Technology (IIT).

Mies sought to establish his own particular architectural style that could represent modern times. His buildings made use of modern materials such as industrial steel and plate glass to define interior spaces. He is often associated with his fondness for the aphorisms "less is more" and "God is in the details".

Mies was born March 27, 1886, in Aachen, Germany. He worked in his father's stone carving shop and at several local design firms before he moved to Berlin, where he joined the office of interior designer Bruno Paul. He began his architectural career as an apprentice at the studio of Peter Behrens from 1908 to 1912, where he was exposed to the current design theories and to progressive German culture. He worked alongside Le Corbusier and Walter Gropius, who was later also involved in the development of the Bauhaus. Mies served as construction manager of the Embassy of the German Empire in Saint Petersburg under Behrens.

Ludwig Mies renamed himself as part of his transformation from a tradesman's son to an architect working with Berlin's cultural elite, adding "van der" and his mother's maiden name "Rohe" and using the Dutch "van der", because the German form "von" was a nobiliary particle legally restricted to those of German nobility lineage. He began his independent professional career designing upper-class homes.

In 1913 Mies married Adele Auguste (Ada) Bruhn (1885–1951), the daughter of a wealthy industrialist. The couple separated in 1918, after having three daughters: Dorothea (1914–2008), an actress and dancer who was known as Georgia, Marianne (1915–2003), and Waltraut (1917–1959), who was a research scholar and curator at the Art Institute of Chicago. During his military service in 1917, Mies fathered a son out of wedlock.

In 1925, Mies began a relationship with designer Lilly Reich that ended when he moved to the United States; from 1940 until his death, artist Lora Marx (1900–1989) was his primary companion. Mies carried on a romantic relationship with sculptor and art collector Mary Callery for whom he designed an artist's studio in Huntington, Long Island, New York. He had a brief romantic relationship with Nelly van Doesburg. After having met in Europe many years prior, they met again in New York in 1947 during a dinner with Josep Lluís Sert where he promised her he would help organize an exhibition in Chicago featuring the work of her late husband Theo van Doesburg. This exhibition took place from October 15 until November 8, 1947, with their romance officially ending not much later. Nevertheless they remained on good terms, spending Easter together in 1948 at a modern farmhouse renovated by Mies on Long Island, as well as meeting several more times that year.

After World War I, while still designing traditional neoclassical homes, Mies began a parallel experimental effort. He joined his avant-garde peers in the long-running search for a new style that would be suitable for the modern industrial age. The weak points of traditional styles had been under attack by progressive theorists since the mid-nineteenth century, primarily for the contradictions of hiding modern construction technology with a facade of ornamented traditional styles.