quality:correction, information:filtering, information:highlighting, linguistic:paraphrasing
Influence

In his time, Hesse was a popular and influential author in the German-speaking world; worldwide fame only came later. Hesse's first great novel, Peter Camenzind, was received enthusiastically by young Germans desiring a different and more "natural" way of life in this time of great economic and technological progress in the country (see also Wandervogel movement). Demian had a strong and enduring influence on the generation returning home from the First World War. Similarly, The Glass Bead Game, with its disciplined intellectual world of Castalia and the powers of meditation and humanity, captivated Germans' longing for a new order amid the chaos of a broken nation following the loss in the Second World War.

Towards the end of his life, German (born Bavarian) composer Richard Strauss (1864–1949) set three of Hesse's poems to music in his song cycle Four Last Songs for soprano and orchestra (composed 1948, first performed posthumously in 1950): "Frühling" ("Spring"), "September", and "Beim Schlafengehen" ("On Going to Sleep").

In the 1950s, Hesse's popularity began to wane, while literature critics and intellectuals turned their attention to other subjects. In 1955, the sales of Hesse's books by his publisher Suhrkamp reached an all-time low. However, after Hesse's death in 1962, posthumously published writings, including letters and previously unknown pieces of prose, contributed to a new level of understanding and appreciation of his works.

By the time of Hesse's death in 1962, his works were still relatively little read in the United States, despite his status as a Nobel laureate. A memorial published in The New York Times went so far as to claim that Hesse's works were largely "inaccessible" to American readers. The situation changed in the mid-1960s when Hesse's works suddenly became bestsellers in the United States. The revival in popularity of Hesse's works has been credited to their association with some of the popular themes of the 1960s counterculture (or hippie) movement. In particular, the quest-for-enlightenment theme of Siddhartha, Journey to the East, and Narcissus and Goldmund resonated with those espousing counter-cultural ideals. The "magic theatre" sequences in Steppenwolf were interpreted by some as drug-induced psychedelia although there is no evidence that Hesse ever took psychedelic drugs or recommended their use. In large part, the Hesse boom in the United States can be traced back to enthusiastic writings by two influential counter-culture figures: Colin Wilson and Timothy Leary. From the United States, the Hesse renaissance spread to other parts of the world and even back to Germany: more than 800,000 copies were sold in the German-speaking world from 1972 to 1973. In a space of just a few years, Hesse became the most widely read and translated European author of the 20th century. Hesse was especially popular among young readers, a tendency which continues today.

There is a quote from Demian on the cover of Santana 's 1970 album Abraxas, revealing the source of the album's title.

Hesse's Siddhartha is one of the most popular Western novels set in India. An authorised translation of Siddhartha was published in the Malayalam language in 1990, the language that surrounded Hesse's grandfather, Hermann Gundert, for most of his life. A Hermann Hesse Society of India has also been formed. It aims to bring out authentic translations of Siddhartha in all Indian languages and has already prepared the Sanskrit, Malayalam and Hindi translations of Siddhartha. One enduring monument to Hesse's lasting popularity in the United States is the Magic Theatre in San Francisco. Referring to "The Magic Theatre for Madmen Only" in Steppenwolf (a kind of spiritual and somewhat nightmarish cabaret attended by some of the characters, including Harry Haller), the Magic Theatre was founded in 1967 to perform works by new playwrights. Founded by John Lion, the Magic Theatre has fulfilled that mission for many years, including the world premieres of many plays by Sam Shepard.

There is also a theatre in Chicago named after the novel, Steppenwolf Theatre.

Throughout Germany, many schools are named after him. The Hermann-Hesse-Literaturpreis is a literary prize associated with the city of Karlsruhe that has been awarded since 1957. Since 1990, the Calw Hermann Hesse Prize has been awarded every two years alternately to a German-language literary journal and a translator of Hesse's work. The Internationale Hermann-Hesse-Gesellschaft (unofficial English name: International Hermann Hesse Society) was founded in 2002 on Hesse's 125th birthday and began awarding its Hermann Hesse prize in 2017.

Musician Steve Adey adapted the poem "How Heavy the Days" on his 2017 LP Do Me a Kindness.

The band Steppenwolf took its name from Hesse's novel.