Like other parts of Continental Europe, the Low Countries are marked in the twentieth century by the two world wars. During World War I, Belgium is the scene of bloody battles between Allied and Axis forces, and during World War II the Low Countries suffer under German occupation.

The two world wars disrupt thriving avant-garde artistic cultures in the Low Countries. At the turn of the century, Belgian artists are at the forefront of the Art Nouveau and Symbolist movements. During the interwar period, Belgian artists René Magritte (1898–1967) and Paul Delvaux (1897–1994) are central to the development of Surrealism. In the Netherlands, De Stijl artists develop abstraction in painting, which has implications for design and architecture as well. Some of the artists associated with De Stijl emigrate to the United States as a consequence of World War II.

In the postwar period, rebuilding projects spark the development of a unique modernist idiom in architecture and design. During the last decades of the century, government investment in good design makes the Netherlands an international leader in the field. Moreover, the particular concern in the Netherlands with the environmental aspects of design and architecture place the Low Countries in the forefront of sustainable development.

• 1898–1900 Architect Victor Horta (1861–1947) builds his own house and studio in Brussels, in the Art Nouveau style for which he is famous. Later, the house will become the Musée Horta.

• 1901 A dress design by the Belgian Henry van de Velde (1863–1957), modeled by his wife, appears in the journal Dekorative Kunst. The design represents van de Velde's interest in the Art Nouveau and Arts and Crafts movements, and epitomizes his comprehensive approach, which encompasses everything from architecture to clothing.

• 1908 The Congo Free State is annexed by Belgium and becomes the African colony of the Belgian Congo. The colony becomes the independent Republic of the Congo in 1960. Between 1971 and 1997, it is known as the Republic of Zaire.

• 1911 Belgian novelist, essayist, and dramatist Maurice Maeterlinck (1862–1949) receives the Nobel Prize for literature. In three books, Maeterlinck explores the mystery of life through studies of various plants and animals: La vie des abeilles (The Life of Bees, 1901), L'intelligence des fleurs (The Intelligence of Flowers, 1907), and La vie des termites (The Life of Termites, 1927).

• 1914–18 Belgian king Albert I (1875–1934) attempts to maintain Belgian neutrality at the time of World War I, but in 1914 is forced to take command of the Belgian army to resist the German invasion. Albert's forces are overwhelmed and he removes his government to Le Havre, France. The Battles of Ypres and Langemarck are fought in Belgium. In 1918, Albert I assumes command of the Belgian army and eventually reenters Brussels triumphant.

• 1914 The war plan of German general Alfred Graf von Schlieffen (1833–1913) violates Luxembourg neutrality, as well as that of Belgium, in pursuit of military victory in France. In addition to the invasion of these two countries, von Schlieffen's plan calls for the invasion of the Netherlands, which is not carried out.

• 1917 Dutch painter Theo van Doesburg (1883–1931) is among the founders of the journal De Stijl, which is the principal organ of the movement of the same name. Its publication continues through 1928. Among the painters associated with the group are the Belgian Georges Vantongerloo (1886–1965) and Dutch painter Piet Mondrian (1872–1944).

• 1917 Dutch architect and designer Gerrit Rietveld (1888–1964) creates the "Red-Blue" chair, which translates the De Stijl technique of composing paintings into the realm of furnishings.

• 1918–33 Architect J. J. P. Oud (1890–1963), among the members of the De Stijl group, serves as official architect of the city of Rotterdam. In this capacity, he demonstrates the applicability of modernist aesthetics and modern materials to the problem of housing construction.

• 1919 Georges Simenon (1903–1989) publishes his first novel, Au pont des arches, in his native Liège, where he is part of a group of young writers and artists who call themselves Les Compagnons de l'Apocalypse (Companions of the Apocalypse). In 1922, Simenon leaves for Paris, where he writes many of his enormously popular novels featuring the detective Inspector Maigret.

• 1920 Piet Mondrian (1872–1944) publishes a manifesto entitled Le Néo-plasticisme (Neoplasticism). The term is synonymous with the De Stijl movement, which brings about the progressive abstraction of painting but also exerts a profound influence on architecture and design internationally.

• 1924–25 Dutch architect Gerrit Rietveld (1888–1964) designs the Schröder House in collaboration with his client Truus Schröder-Schräder (1889–1985). The building adapts aspects of De Stijl painting to architecture at the same time that it responds to the unique requirements of the patron, a single woman with children.

• 1926 The Draps family begins a workshop for high-end chocolate production in Bussels. Later, the company becomes known as Godiva and exports its product worldwide.

• 1927 Belgian painter René Magritte (1898–1967) has his first exhibition in Brussels. In 1928–29, he produces one of his best-known works, The Treachery of Images (Los Angeles County Museum of Art), a painting of a pipe bearing the caption "Ceci n'est pas une pipe" ("This is not a pipe"), which embodies his association with the Surrealist movement.

• 1928–31 The Raadhuis (Town Hall) of Hilversum, the Netherlands, is built to the design of Willem Dudok (1884–1974). The building demonstrates the impact of American Prairie-style architecture in the Netherlands and is also part of Dudok's project to plan the expansion of the city of Hilversum.

• 1929 Georges Remi (1907–1983), a Belgian writer and artist better known as "Hergé," begins work on a series of comic books called The Adventures of Tintin. Both the main character and Hergé's ligne claire (clear line) illustration style become well known internationally.

• 1929 Belgian painter James Ensor (1860–1949) exhibits his most famous work, Christ's Entry into Brussels (1888; Getty Museum, Los Angeles), publicly for the first time. In the same year, he is made a baron by King Albert I (1875–1934).

• 1934 Leopold III (1901–1983) succeeds his father as king of the Belgians. He becomes a controversial figure after his surrender to Germany in 1940, eighteen days after Germany's invasion of Belgium. In 1944, Leopold and his family are taken prisoners in Germany and liberated by American troops in 1945. Although Leopold is exonerated of charges of treason, he goes into exile in Switzerland, returning to Belgium in 1950 and abdicating the following year.

• 1938 The Rijksmuseum Kröller-Müller is founded in Otterlo, the Netherlands, and houses a collection of nineteenth- and twentieth-century art.

• 1940 The Netherlands is occupied by Nazi German forces. The royal family flees to Britain and then to Canada, returning with the end of World War II in 1945. Belgium is also invaded by Germany in 1940. There, the resistance to the German invaders is led by the White Brigade and the Secret Army.

• 1941 Dutch graphic artist M. C. Escher (1898–1972) settles in Baarn, the Netherlands, following a period of dislocation in Italy, Belgium, and Switzerland brought about, in part, by World War II. Escher is widely known for his drawings based on the use of perspective, geometric forms, and optical tricks.

• 1946 The Dutch Vrij Beelden (Free Images) avant-garde art movement is founded. Along with the Creatie movement (1950–55), it will later become incorporated into the COBRA movement (derived from the names of the members' home cities: Copenhagen, Brussels, and Amsterdam). Among the artists associated with COBRA are the Dutch painter Karel Appel (born 1921) and the Belgian painter Pierre Alechinsky (born 1927).

• 1947 The wartime diary of Annelies Marie "Anne" Frank (1929–1945) is published posthumously as Het achterhuis and in English in 1952 as The Diary of a Young Girl. In 1956, Frank's chronicles of her years in hiding during the Nazi occupation of the Netherlands is adapted as a Pulitzer Prize–winning play, The Diary of Anne Frank, and in 1959 is released as a motion picture.

• 1947 Han van Meegeren (1889–1947) is tried for forgery in a very public proceeding that makes him the second most well-known man in the Netherlands, after the prime minister. Van Meegeren is known for his convincing forgeries of Dutch master paintings sold to Nazi officials and other buyers during World War II.

• 1958 Belgian comic-book artist Pierre Culliford (1928–1992), who goes by the name of "Peyo," draws his first "Smurf" in the "Johan et Pirlouit" comic. The Smurfs star in the 1976 animated feature film La flûte à six schtroumpfs, with music by French composer Michel Legrand (born 1932), and become known to Anglophones through an American television cartoon series that first airs in 1981.

• 1965 Belgian conceptual artist Panamarenko (born 1940) produces collages for Happening News connected with Happenings in Antwerp. In 1967, he builds his first flying machine, Flugzeug. Later utopian contraptions include a diving suit, balloon, and camel.

• 1968 Belgian artist Marcel Broodthaers (1924–1976) exhibits the work Musée d'Art Moderne, Département des Aigles, Section Publicité in his home. In this and other works, many of which incorporate found objects, he calls into question the institutions that surround the production and consumption of art.

• 1973 Dutch architect Aldo van Eyck (1918–1999) designs the Hubertushuis in Amsterdam, which is not completed until 1981. The building provides temporary shelter for single parents and children and embodies van Eyck's critique of modernism, also indicated by his founding membership in Team X, a group of young architects established in 1953 in opposition to orthodox modernist architecture and planning.

• 1973 The Rijksmuseum Vincent van Gogh in Amsterdam, for which initial sketches were made by Gerrit Rietveld (1888–1964) and the design completed by his architectural partners, opens to the public. The Exhibition Wing, designed by Kisho Kurokawa (born 1934), is added in 1999.

• 1980 Beatrix Wilhelmina Armgard of Orange-Nassau (born 1938) becomes queen of the Kingdom of the Netherlands following the abdication of her mother, Juliana Louise Emma Marie Wilhelmina, duchess of Mecklenburg-Schwerin (1909–2004), who ruled from 1948.

• 1982 The novel De Aanslag (The Assault) by Harry Mulisch (born 1927), an Amsterdam-based writer, is published. In 1986. It becomes the basis of an Academy Award—winning film of the same name that brings Mulisch international recognition.

• 1984–87 Rem Koolhaas (born 1944), working with the Office for Metropolitan Architecture (OMA), designs the Netherlands Dance Theater in the Hague. The building represents a type of contemporary architecture known as "Deconstructionist," which has strong ties to contemporary literary and aesthetic theory. Koolhaas wins the Pritzker Architecture Prize in 2000.

• 1988 Ben van Berkel (born 1957) and Caroline Bos (born 1959) establish an architectural practice in Amsterdam. Later, they found UN Studio, an architecture and urban planning collaborative. Van Berkel becomes the design architect for the expansion and renovation of the Wadsworth Athenaeum in Hartford, Connecticut, in 1999.

• 1993 The Droog Design movement begins with an exhibition at the Milan Furniture Fair, including the "Crossing Italy I" couch by Richard Hutten (born 1967). The movement, which at first includes only Dutch designers, is codified by jewelry designer Gijs Bakker (born 1942) and critic Renny Ramakers, both associated with the Nieuwe Abstractie (New Abstraction) design movement of the 1960s and '70s.

• 1993–99 The Netherlands Design Institute supports the integration of and collaboration between designers, producers, and educational institutions.

• 1994 The Dutch Electronic Art Festival is established in Rotterdam. The biennial festival features a variety of exhibitions, installations, and performances.

• 1996 The Contemporary Design from the Netherlands exhibition is held at the Museum of Modern Art, New York. Among the featured designers are Ed Annink (born 1956), Gijs Bakker (born 1942), and Rody Graumans (born 1968).

• 1999 The Nike European Headquarters building is completed in Hilversum, the Netherlands, by the American architectural firm William McDonough + Partners. The building incorporates environmentally conscious elements and embodies the widespread commitment in the Netherlands to sustainable architecture.