Rudolf Joseph Lorenz Steiner (25 or 27 February 1861 – 30 March 1925) was an Austrian philosopher, social thinker, architect and esotericist. He gained initial recognition as a literary critic and cultural philosopher. At the beginning of the twentieth century, he founded a new spiritual movement, Anthroposophy, as an esoteric philosophy growing out of European transcendentalism and with links to Theosophy.

Steiner led this movement through several phases. In the first, more philosophically oriented phase, Steiner attempted to find a synthesis between science and mysticism; his philosophical work of these years, which he termed spiritual science, sought to provide a connection between the cognitive path of Western philosophy and the inner and spiritual needs of the human being. In a second phase, beginning around 1907, he began working collaboratively in a variety of artistic media, including drama, the movement arts (developing a new artistic form, eurythmy) and architecture, culminating in the building of a cultural center to house all the arts, the Goetheanum. After the First World War, Steiner worked with educators, farmers, doctors, and other professionals to develop Waldorf education, biodynamic agriculture, anthroposophical medicine as well as new directions in numerous other areas. Steiner advocated a form of ethical individualism, to which he later brought a more explicitly spiritual component. He based his epistemology on Johann Wolfgang Goethe's world view, in which “Thinking … is no more and no less an organ of perception than the eye or ear. Just as the eye perceives colours and the ear sounds, so thinking perceives ideas.” A consistent thread that runs from his earliest philosophical phase through his later spiritual orientation is the goal of demonstrating that there are no essential limits to human knowledge.

Steiner's father, Johann(es) (Baptist) Steiner (June 23, 1829, Geras (or Trabenreith, Irnfritz-Messern), and lived Geras Abbey, Waldviertel - 1910, Horn), left a position as huntsman in the service of Count Hoyos in Geras, northest Lower Austria to marry Franziska Blie (May 8, 1834, Horn, Waldviertel - 1918, Horn), a marriage for which the Count had refused his permission. Johann became a telegraph operator on the Southern Austrian Railway, and at the time of Rudolf's birth was stationed in Kraljevec in the Muraköz region, then part of the Austro-Hungarian Empire (present-day Donji Kraljevec, Međimurje region, northernmost Croatia). In the first two years of Rudolf's life, the family moved twice, first to Mödling, near Vienna, and then, through the promotion of his father to station master, to Pottschach, located in the foothills of the eastern Austrian Alps in present day Burgenland.

From 1879 to 1883, Steiner attended and then graduated from the Vienna Institute of Technology (Technische Hochschule), where he studied mathematics, physics, and philosophy. In 1882, one of Steiner's teachers at the university in Vienna, Karl Julius Schröer, suggested Steiner's name to Joseph Kürschner, editor of a new edition of Goethe's works. Steiner was then asked to become the edition's scientific editor.

In his autobiography, Steiner related that at 21, on the train between his home village and Vienna, he met a simple herb gatherer, Felix Koguzki, who spoke about the spiritual world "as one who had his own experience therein..." This herb gatherer introduced Steiner to a person that Steiner only identified as a “master”, and who had a great influence on Steiner's subsequent development, in particular directing him to study Fichte's philosophy.

In 1891, Steiner earned a doctorate in philosophy at the University of Rostock in Germany with a thesis based upon Fichte's concept of the ego, later published in expanded form as Truth and Knowledge.

In 1888, as a result of his work for the Kürschner edition of Goethe's works, Steiner was invited to work as an editor at the Goethe archives in Weimar. Steiner remained with the archive until 1896. As well as the introductions for and commentaries to four volumes of Goethe's scientific writings, Steiner wrote two books about Goethe's philosophy: The Theory of Knowledge Implicit in Goethe's World-Conception (1886) and Goethe's Conception of the World (1897). During this time he also collaborated in complete editions of Arthur Schopenhauer's work and that of the writer Jean Paul and wrote numerous articles for various journals. During his time at the archives, Steiner wrote what he considered his most important philosophical work, Die Philosophie der Freiheit (The Philosophy of Freedom) (1894), an exploration of epistemology and ethics that suggested a path upon which humans can become spiritually free beings.

In 1896, Elisabeth Förster-Nietzsche asked Steiner to set the Nietzsche archive in Naumburg in order. Her brother by that time was non compos mentis. Förster-Nietzsche introduced Steiner into the presence of the catatonic philosopher and Steiner, deeply moved, subsequently wrote the book Friedrich Nietzsche, Fighter for Freedom. Of Nietzsche, Steiner says in his autobiography, “Nietzsche's ideas of the ‘eternal recurrence' and of ‘Übermensch' remained long in my mind. For in these was reflected that which a personality must feel concerning the evolution and essential being of humanity when this personality is kept back from grasping the spiritual world by the restricted thought in the philosophy of nature characterizing the end of the nineteenth century.” "What attracted me particularly was that one could read Nietzsche without coming upon anything which strove to make the reader a 'dependent' of Nietzsche's."

In 1897, Steiner left the Weimar archives and moved to Berlin. He became owner, chief editor, and active contributor to the literary journal Magazin für Literatur, where he hoped to find a readership sympathetic to his philosophy. His work in the magazine was not well received by its readership, including the alienation of subscribers following Steiner's unpopular support of Émile Zola in the Dreyfus Affair. The journal lost more subscribers when Steiner published extracts from his correspondence with anarchist writer John Henry Mackay. Dissatisfaction with his editorial style eventually led to his departure from the magazine.

In 1899, Steiner married Anna Eunicke; they were later separated. Anna died in 1911.

In 1899, Steiner published an article in his Magazin für Literatur, titled “Goethe's Secret Revelation”, on the esoteric nature of Goethe's fairy tale, The Green Snake and the Beautiful Lily. This article led to an invitation by the Count and Countess Brockdorff to speak to a gathering of Theosophists on the subject of Nietzsche. Steiner continued speaking regularly to the members of the Theosophical Society, becoming the head of its newly constituted German section in 1902 without ever formally joining the society. It was within this society that Steiner met and worked with Marie von Sivers, who became his second wife in 1914. By 1904, Steiner was appointed by Annie Besant to be leader of the Theosophical Esoteric Society for Germany and Austria. The German Section of the Theosophical Society grew rapidly under Steiner's leadership as he lectured throughout much of Europe on his spiritual science. During this period, Steiner maintained an original approach, replacing Madame Blavatsky's terminology with his own, and basing his spiritual research and teachings upon the Western esoteric and philosophical tradition. This and other differences, in particular Steiner's vocal rejection of C.W. Leadbeater and Annie Besant's pronouncement that Jiddu Krishnamurti was the vehicle of a new world teacher and the reincarnation of Christ, led to a formal split in 1912/13, when Steiner and the majority of members of the German section of the Theosophical Society broke off to form a new group, the Anthroposophical Society.

The Anthroposophical Society grew rapidly. Fueled by a need to find a home for their yearly conferences, which included performances of plays written by Eduard Schuré as well as Steiner himself, the decision was made to build a theater and organizational center. In 1913, construction began on the first Goetheanum building, in Dornach, Switzerland. The building, designed by Steiner, was built to a significant part by volunteers who offered craftsmanship or simply a will to learn new skills. Once World War I started in 1914, the Goetheanum volunteers could hear the sound of cannon fire beyond the Swiss border, but despite the war, people from all over Europe worked peaceably side by side on the building's construction.

Beginning in 1919, Steiner was called upon to assist with numerous practical activities, including the first Waldorf school, founded that year in Stuttgart, Germany. His lecture activity expanded enormously. At the same time, the Goetheanum developed as a wide ranging cultural centre. On New Year's Eve, 1922/1923, it was burned down by arson; only his massive sculpture depicting the spiritual forces active in the world and the human being, the Representative of Humanity, was saved. Steiner immediately began work designing a second Goetheanum building – made of concrete instead of wood – which was completed in 1928, three years after his death.

During the Anthroposophical Society's Christmas conference in 1923, Steiner founded a School of Spiritual Science, intended as an open university for research and study. This university, which has various sections or faculties, has grown steadily; it is particularly active today in the fields of education, medicine, agriculture, art, natural science, literature, philosophy, sociology and economics. Steiner spoke of laying the foundation stone of the new society in the hearts of his listeners, while the First Goetheanum's foundation stone had been laid in the earth. He gave a Foundation Stone meditation to anchor this.

The arson committed against the First Goetheanum had a context. Threats had been made publicly against the Goetheanum, and against Steiner himself by right-wing nationalists.

Reacting to the catastrophic situation in post-war Germany, Steiner had gone on extensive lecture tours promoting his social ideas of the Threefold Social Order, entailing a fundamentally different political structure; he suggested that only through independence of the cultural, political and economic realms could such catastrophes as the World War be avoided. He also promoted a radical solution in the disputed area of Upper Silesia - claimed by both Poland and Germany: his suggestion that this area be granted at least provisional independence led to his being publicly accused of being a traitor to Germany.

In 1919, the political theorist of the National Socialist movement in Germany, Dietrich Eckart, attacked Steiner and suggested that he was a Jew. In 1921, Adolf Hitler attacked Steiner in an article in the right-wing Völkischen Beobachter newspaper, including accusations that Steiner was a tool of the Jews, and other nationalist extremists in Germany called up a "war against Steiner". The 1923 Beer Hall Putsch in Munich led Steiner to give up his residence in Berlin, saying that if those responsible for the attempted coup [Hitler and others] came to power in Germany, it would no longer be possible for him to enter the country; he also warned against the disastrous effects it would have for Central Europe if the National Socialists came to power.

The loss of the Goetheanum affected Steiner's health seriously. From 1923 on, he showed signs of increasing frailness and illness. He continued to lecture widely, and even to travel; especially towards the end of this time, he was often giving two, three or even four lectures daily for courses taking place concurrently. Many of these were for practical areas of life; simultaneously, however, Steiner began an extensive series of lectures presenting his research on the successive incarnations of various individualities, and on the technique of karma research generally. Increasingly ill, his last lecture was held in September, 1924. He continued to write on his autobiography during the last months of his life; he died on 30 March 1925.

From 1899 until his death in 1925, Steiner articulated an ongoing stream of experiences that he claimed were of the spiritual world — experiences he said had touched him from an early age on. Steiner aimed to apply his training in mathematics, science, and philosophy to produce rigorous, verifiable presentations of those experiences. Steiner believed that through freely chosen ethical disciplines and meditative training, anyone could develop the ability to experience the spiritual world, including the higher nature of oneself and others. Steiner believed that such discipline and training would help a person to become a more moral, creative and free individual - free in the sense of being capable of actions motivated solely by love.

Steiner's ideas about the inner life were influenced by Franz Brentano, with whom he had studied, and Wilhelm Dilthey, both founders of the phenomenological movement in European philosophy, as well as the transcendentalist stream in German philosophy represented by Fichte, Hegel, and Schelling. Steiner was also influenced by Goethe's phenomenological approach to science.