Marilyn Ferguson (born 1938, Grand Junction, Colorado) is a New Age American author and public speaker. She wrote the bestselling The Brain Revolution (Taplinger, 1973). In 1975 she founded Brain/Mind Bulletin, a monthly publication, to create an ongoing dialogue for new discoveries across multidisciplinary fields. Bulletin subscriptions quickly multiplied and came to span 52 countries (as of 2007). The Bulletin was largely responsible for popularizing some of the most significant scientific paradigm shifts of the 20th century.

Ferguson's 1980 The Aquarian Conspiracy (JP Tarcher, 1980; 1987) chronicled the activities of an enthusiastic network of eminent and powerful movers and shakers from diverse fields working to bring about radical change and create a more cooperative society through “a benign conspiracy for a new human agenda”. The New York Times described this movement as “an alternative thought ... working its way increasingly into the nation’s cultural, religious, social, economic, and political life.” Ferguson's manifesto is widely credited as pulling into focus and giving impetus to “the great irrevocable shift” she so vividly described and helped to foment. The Aquarian Conspiracy, which USA Today hailed as “the handbook of the New Age”, was translated into dozens of languages and sold millions of copies world-wide. The book has remained in print for nearly three decades. The Aquarian Conspiracy was voted “the most significant political book of the decade” by readers of the alternative press. It garnered numerous honors, including being named among the ten most important books of the 20th Century in 1999. She is a founding member of the Association of Humanistic Psychology, and serves on the board of directors of The Institute of Noetic Science. She was awarded the “Library Trust Award” from Brandeis University, an honorary D.Litt from John F. Kennedy University, and the “Brain Trainer of the Year Award” from the American Society for Training and Development. The Aquarian Conspiracy prompted Al Gore, while still a United States Senator, to found the Congressional Clearinghouse on the Future, to establish a forum for introducing policymakers in Washington to ideas and insights from the private sector. The vast success of her book helped create a movement in American publishing during the 1980s/1990s that would come to be known as the widely popular New Age genre.