Alan Leo, born William Frederick Allan, (7 August 1860 – 30 August 1917) was an English astrologer, author, publisher, astrological data collector and theosophist. He is often referred to as "the father of modern astrology".

His work stimulated a revival of astrology in the Western world after its decline at the end of the 17th century. Leo was a devout theosophist and he worked many of its religious concepts such as karma and reincarnation into his astrology. He used the Theosophical Society's vast international connections to publish, translate and disseminate his work across Europe and America.

Astrological technique and influence

thumb|left|200px|Alan Leo's [[natal chart]]

Leo was born in Westminster, and took the name of his sun-sign as a pseudonym, is credited with starting the movement towards a more psychologically-oriented horoscope analysis in astrology, being the first astrologer to argue for a loose interpretation of possible trends of experience rather than the specific prediction of events. His influence has been described as marking a 'turning point' in horoscope delineation, because, as astrological historian James Holden explains:

In 1890, Leo invited George R.S. Mead to found an occult lodge in Brixton, South London. Towards the end of his life, in 1909, and again in 1911, Leo travelled with his wife Bessie Leo to India where he studied Indian astrology.

Leo was a non-smoker, teetotaller and vegetarian. In 1915, Leo founded the Astrological Lodge of London.

In 1914, aged 54, Leo faced prosecution against the charge that he "did unlawfully pretend to tell fortunes" through astrology. The case was dismissed for lack of evidence, but it led to Leo's belief that astrology needed to be revised to be legitimised. His advice to fellow astrologers was:

In 1917 Leo stood trial again on a similar charge. Despite his insistence that he told only "tendencies" and not "fortunes", he lost his case and was fined £5 plus costs. He died a few weeks later from an apoplexy (cerebral haemorrhage), at 10:00 am on 30 August 1917, whilst on a holiday at Bude in Cornwall, which was intended to restore his health after the ordeals of the trial.