A golem, perhaps the best known of the Jewish legends, is an automaton, typically humanoid and typically male, created as the result of an intense, systematic, mystical meditation. The word golem means (or implies) something unformed and imperfect, or a body without a soul. The word appears once in the Bible, in Psalms 139:15-16.
The best-known tales of the golem concern one Rabbi Yehuda Loew, the Marharal of Prague, who created the mythical being to protect the Jews from blood libels and plots often instigated by the priest Thaddeus. This story, in all of its variants, may be one you're familiar with. But quite a number of Kabbalists, both practical and theoretical, have discussed the golem, from the Talmudic era on, in both physical and purely mystical contexts.
Early History: The Golem and "Sefer Yetzitah"
Stories of artificial creations made by Jewish sages appear very early, during the Talmudic era (prior to 500 C.E.). In theological discussions, Adam is described as a golem during the time of his formation, but prior to God blowing life and (more importantly) soul into him.
By another early account Rava and Rabbi Zeira, through their meditations, created a calf, which they then slaughtered and ate; in another variant, Rabbis Khanina and Hoshaya did the same, just before each Sabbath.
The power of the written word, Torah, Hebrew alphabet, and the Names of God were well-known to these people, and it was believed that the secrets of the universe were locked within them. These hidden knowledges included the power of creation. Those who wished to study this sort of thing had a handbook: the Sefer Yetzira, the Book of Creation.
The golem and its creation not explicitly mentioned or discussed in the Sefer Yetzira, yet this small volume is of immense importance to the Kabbalists (theoretical and practical), and it sets up the framework which makes the idea and potential of a golem possible.
Written between the third and six centuries, Sefer Yetzira is short, enigmatic book which proposes to explain God's creation of the universe, including the construction of the world and cosmos, by means of the Sefirot (divine emanations) and Hebrew alphabet. Letters are divided up into categories which parallel elements, seasons, parts of the body, heavens, etc., the premise being that the combinations of these letters and the Divine Name form the structure of all things, good and evil. In a sense, it suggests a divine periodic table or divine atoms. Theoretically, one who understands the means may then apply them to their own creative ends. It was by meditating on Sefer Yetzira (for up to three years, by a number of accounts), that pious mystics like Rava were able to create their own creatures.
Many translations of and commentaries on the Sefer Yetzira exist, from ancient times to modern. Since a full discussion of it is currently outside the scope of this site, I suggest referring to Gershom Sholem for commentary and history, and for a translation with commentary, Aryeh Kaplan.
Where the creation of a golem is concerned, mystics based their techniques on their own interpretations of the book.
The golem has been a popular subject in literature, appearing in many folktales, novels, children's books, and plays. It has inspired music, plays, and movies. It was even the subject of a tragic and creepy episode of "The X Files". (In which a librarian tells Mulder, incorrectly, that the Sefer Yetzira discusses the golem and how to create one.)
The tales concerning Rabbi Loew of Prague (born 1513) did not become popular until the eighteenth century. Though he did comment on Sefer Yetzira and the story of Rava's created man, the popular stories about Yosele Golem have no historical basis and little relationship to the life and times of Loew. Yudl Rosenberg published what was supposedly a 300 year-old manuscript about Loew and the golem in 1909, though he never produced his source and many now believe he was in fact the author.
The stories of Loew are most likely related to those of Elija of Chelm. In these older stories, powered by the Name of God, the golem continues to grow larger and larger each day, until Elija fears it will outgrow the house and become dangerous. It's a close call; the creature becomes so large and unruly Elija is barely able to reach up to remove the Name. Elija of Chelm was a real man, a contemporary of Loew, and the story of the golem was passed down through the generations of his family. It seems likely Elija's story was "transferred" to Loew, but why is not entirely clear.
In Gustav Meyrink's novel Der Golem (published serially 1913-14, as a book in 1915), the golem actually has little to do with the story, appearing to the main character only a couple of times early in the book. When he appears to the protagonist, Pernath, a man who cannot remember his past, the plot is set in motion. It seems as if the golem, a mystery of the past, here represents the lost years and blank slate Pernath has become, or his state of mind: he simply goes through the motions of life without really understanding who he is. Or one could say Pernath is the golem, "unformed", robbed of his soul by madness and psychiatric treatment.
I found this variation of the WWII tale posted by Avrohom Shlomo Levy on the B'Nei Baruch internet discussion forum, 6/8/97:
Commenting that the golem is not a miracle, monster, or natural, but something entirely apart, Moshe Idel writes, "It is an entity that serves the role of silent witness of the creativity inherent in the tools which served God and men in their creative endeavors."