As a Man Thinketh is a self-help book by James Allen, published in 1903. James insists upon the power of the individual to form his own character and to create his own happiness. This work shows how, in his own thought-world, each man holds the key to every condition, good or bad, that enters into his life, and that, by working patiently and intelligently upon his thoughts, he may remake his life, and transform his circumstances.

It was also described by Allen as a book that will help you to help yourself, a pocket companion for thoughtful people, and a book on the power and right application of thought.

James Allen (28 November 1864 - 24 January 1912) was a British philosophical writer known for his inspirational books and poetry and as a pioneer of the self-help movement. His best known work, As a Man Thinketh, has been mass-produced since its publication in 1903. It has been a source of inspiration to motivational and self-help authors.