As a Man Thinketh is an inspirational book by James Allen, first published in 1903. It deals with the power of thought, and particularly with the use and application of thought to create happy and prosperous circumstances. The writing is simple, so that all can easily grasp the teachings and put the methods into practice. It shows how each person holds the key to every condition in their lives, and how, by working patiently and intelligently upon their thoughts, they may remake their circumstances.

In the earlier work, From Poverty to Power: The Realization of Prosperity and Peace (1901) Allen emphasizes that a disciplined mind and a focus on serving others are the keys to achieving prosperity. This one has a stronger focuses on the individual’s state of mind, contemplation and inner investigation, and concludes with the theme that selflessness is the path to unconditional love.