Friedrich Stowasser (15 December 1928 – 19 February 2000), better known by his pseudonym Friedensreich Regentag Dunkelbunt Hundertwasser, was an Austrian visual artist and architect who also worked in the field of environmental protection.

Hundertwasser stood out as an opponent of "a straight line" and any standardization, expressing this concept in the field of building design. His best known work is the Hundertwasserhaus in Vienna, which has become a notable place of interest in the Austrian capital, characterised by imaginative vitality and uniqueness. The Nazi era was a very difficult time for Hundertwasser and his mother Elsa, who were Jewish. They avoided persecution by posing as Christians, a credible ruse as Hundertwasser's father had been a Catholic. Hundertwasser was baptized as a Catholic in 1935. To remain inconspicuous, Hundertwasser also joined the Hitler Youth.

Hundertwasser developed artistic skills early on. After the war, he spent three months at the Academy of Fine Arts in Vienna. At this time, he began to sign his art as Hundertwasser instead of Stowasser. He left to travel, using a small set of paints he carried at all times to sketch anything that caught his eye. In Florence, he met the young French painter René Brô for the first time and they became lifelong friends. Hundertwasser's first commercial painting success was in 1952–53 with an exhibition in Vienna.His adopted surname is based on the translation of "sto" (the Slavic word for "(one) hundred") into German. The name Friedensreich has a double meaning as "Peace-realm" or "Peace-rich" (in the sense of "peaceful"). Therefore, his name Friedensreich Hundertwasser translates directly into English as "Peace-Realm Hundred-Water". The other names he chose for himself, Regentag and Dunkelbunt, translate to "Rainy day" and "Darkly multi-coloured".

In the early 1950s, he entered the field of architecture. Hundertwasser also worked in the field of applied art, creating flags, stamps, coins, and posters. His most famous flag is his koru flag (designed in 1983), as well as several postage stamps for the Austrian Post Office. He also designed stamps for Cape Verde and for the United Nations postal administration in Geneva on the occasion of the 35th anniversary of the Universal Declaration of Human Rights.

In 1957 Hundertwasser acquired a farm on the edge of Normandy. Hundertwasser married Herta Leitner in 1958 but they divorced two years later. He married again in 1962 to the Japanese artist Yuko Ikewada but she divorced him in 1966. By this time, he had gained a popular reputation for his art.

In 1964 Hundertwasser bought "Hahnsäge", a former saw mill, in the sparsely populated Lower Austria's Waldviertel. There, far from the hustle and bustle and surrounded by nature, he set up a new home.

He spent some time in the 1960s in the Tooro Kingdom in Uganda, Central Africa, where he painted a number of works and named them after the kingdom.

In 1972 Hundertwasser incorporated a stock company, the "Grüner Janura AG", in Switzerland; in 2008 it was renamed as "Namida AG". Hundertwasser managed his intellectual property rights through this company.

In the 1970s, Hundertwasser acquired several properties in the Bay of Islands in New Zealand, which include a total area of approximately 372 ha of the entire "Kaurinui" valley. There he realized his dream of living and working closely connected to nature. Beside other projects he designed the "Bottle House" there. He could live largely self-sufficiently using solar panels, a water wheel and a biological water purification plant. His first grass roof experiments took place there.

In 1979 Hundertwasser bought the vast historical garden Giardino Eden ('Garden of Eden') in Venice, including the Palazzo Villa delle Rose, from Alexandra of Yugoslavia via his Swiss company.

In 1980, Hundertwasser visited Washington D.C. to support activist Ralph Nader's efforts to oppose nuclear proliferation. Mayor Marion Barry declared 18 November to be Hundertwasser Day as a result. Hundertwasser planted trees in Judiciary Square and advocated on behalf of a co-op apartment owner who was taken to court for installing a bay window.

In 1982, Hundertwasser's only child, his daughter Heidi Trimmel, was born.

Hundertwasser died on February 19 2000, on board Queen Elizabeth II from a heart attack. According to his wish he was buried in harmony with nature on his land in New Zealand, in the Garden of the Happy Dead under a Tulip Tree.

Hundertwasser's original and unruly artistic vision expressed itself in pictorial art, environmentalism, philosophy, and design of facades, postage stamps, flags, and clothing (among other areas). The common themes in his work utilised bright colours, organic forms, a reconciliation of humans with nature, and a strong individualism, rejecting straight lines.

He remains sui generis, although his architectural work is comparable to Antoni Gaudí (1852–1926) in its use of biomorphic forms and the use of tile. He was also inspired by the art of the Vienna Secession, and by the Austrian painters Egon Schiele (1890–1918) and Gustav Klimt (1862–1918).

He was fascinated by spirals, and called straight lines "godless and immoral" and "something cowardly drawn with a rule, without thought or feeling"He c alled his theory of art "transautomatism", focusing on the experience of the viewer rather than the artist.This was encapsulated by his design of a new flag for New Zealand, which incorporated the image of the Koru a spiral shape based on the image of a new unfurling silver fern frond and symbolizing new life, growth, strength and peace according to the Māori people.

Even though Hundertwasser first achieved notoriety for his boldly-coloured paintings, he is more widely known for his individual architectural designs. These designs use irregular forms, and incorporate natural features of the landscape. The Hundertwasserhaus apartment block in Vienna has undulating floors ("an uneven floor is a melody to the feet"), a roof covered with earth and grass, and large trees growing from inside the rooms, with limbs extending from windows. He took no payment for the design of Hundertwasserhaus, declaring that it was worth the investment to "prevent something ugly from going up in its place".

From the early 1950s he increasingly focused on architecture, advocating more just human and environmental friendly buildings. This began with manifestos, essays and demonstrations. For example, he read out his "Mouldiness Manifesto against Rationalism in Architecture" in 1958 on the occasion of an art and architectural event held at the Seckau Monastery. He rejected the straight line and the functional architecture.In Munich in 1967 he gave a lecture called "Speech in Nude for the Right to a Third Skin". His lecture "Loose from Loos, A Law Permitting Individual Buildings Alterations or Architecture-Boycott Manifesto", was given at the Concordia Press Club in Vienna in 1968.

In the Mouldiness Manifesto he first claimed the "Window Right": "A person in a rented apartment must be able to lean out of his window and scrape off the masonry within arm's reach. And he must be allowed to take a long brush and paint everything outside within arm's reach. So that it will be visible from afar to everyone in the street that someone lives there who is different from the imprisoned, enslaved, standardised man who lives next door."[13] In his nude speeches of 1967 and 1968 Hundertwasser condemned the enslavement of humans by the sterile grid system of conventional architecture and by the output of mechanised industrial production. He rejected rationalism, the straight line and functional architecture.

For Hundertwasser, human misery was a result of the rational, sterile, monotonous architecture, built following the tradition of the Austrian architect Adolf Loos, author of the modernist manifesto Ornament and crime (1908). He called for a boycott of this type of architecture, and demanded instead creative freedom of building, and the right to create individual structures. In 1972 he published the manifesto Your window right — your tree duty. Planting trees in an urban environment was to become obligatory: "If man walks in nature's midst, then he is nature's guest and must learn to behave as a well-brought-up guest." Hundertwasser propagated a type of architecture in harmony with nature in his ecological commitment. He campaigned for the preservation of the natural habitat and demanded a life in accordance with the laws of nature. He wrote numerous manifestos, lectured and designed posters in favor of nature protection, including against nuclear power, to save the oceans and the whales and to protect the rain forest. He was also an advocate of composting toilets and the principle of constructed wetland. He perceived feces not as nauseous but as part of the cycle of nature. His beliefs are testified by his manifesto The Holy Shit and his DIY guide for building a composting toilet.

In the 1970s, Hundertwasser had his first architectural models built. The models for the Eurovision TV-show "Wünsch Dir was" (Make a Wish) in 1972 exemplified his ideas on forested roofs, tree tenants and the window right. In these and similar models he developed new architectural shapes, such as the spiral house, the eye-slit house, the terrace house and the high-rise meadow house. In 1974, Peter Manhardt made models for him of the pit-house, the grass roof house and the green service station – along with his idea of the invisible, inaudible Green Motorway.

In the early 1980s Hundertwasser remodelled the Rosenthal Factory in Selb, and the Mierka Grain Silo in Krems. These projects gave him the opportunity to act as what he called an "architecture doctor".[citation needed]

In architectural projects that followed he implemented window right and tree tenants, uneven floors, woods on the roof, and spontaneous vegetation.[citation needed] Works of this period include: housing complexes in Germany; a church in Bärnbach, Austria; a district heating plant in Vienna; an incineration plant and sludge centre in Osaka, Japan; a railway station in Uelzen; a winery in Napa Valley; and the Hundertwasser toilet in Kawakawa, New Zealand.

In 1999 Hundertwasser started his last project named Die Grüne Zitadelle von Magdeburg (in German). Although he never completed this work, the building was built a few years later in Magdeburg, a town in eastern Germany, and opened on 3 October 2005.