William Quan Judge (April 13, 1851 – March 21, 1896) was an Irish-American mystic, esotericist, and occultist, and one of the founders of the original Theosophical Society. He was born in Dublin, Ireland. When he was 13 years old, his family emigrated to the United States. He became a naturalized citizen of the USA at age 21 and passed the New York state bar exam, specializing in commercial law.

Judge was one of the seventeen co-founders of the Theosophical Society. Like Helena Petrovna Blavatsky and Henry Steel Olcott, he stayed in the organization when others left. When Olcott and Blavatsky left the United States for India, he stayed behind to manage the Society's work, all the while working as a lawyer.

When Blavatsky and Olcott left America, they left Theosophy in North America in Judge's hands. While Judge kept in close contact with both Blavatsky and Olcott through correspondence, there was little if any organized activity for the next several years. His difficulties over this period of time are illustrated by a biographical passage written by Mrs. Archibald Keightley: "It was a time when Madame Blavatsky – she who was then the one great exponent, had left the field ... the interest excited by her ... striking mission had died down. The T.S. was henceforth to subsist on its philosophical basis ... From his twenty-third year until his death, (Mr. Judge's) best efforts and all the fiery energies of his undaunted soul were given to this work."

In 1876, business affairs caused him to visit South America, where he contracted "Chagres fever", and he was ever after a sufferer from that torturing disease. Other "phases" of his experiences on this journey are recorded in his writings, often allegorical, suggesting the character of the occult contacts which may have been established on this journey. [Wikipedia]