Ralph Herman Abraham (born July 4, 1936) is an American mathematician. He has been a member of the faculty of the University of California, Santa Cruz (where he is currently professor emeritus of mathematics) since 1968. Abraham has been involved in the development of dynamical systems theory since the 1960s and 1970s. He has been a consultant on chaos theory and its applications in numerous fields, such as medical physiology, ecology, mathematical economics, psychotherapy, etc. He credits his use of the psychedelic drug DMT for "swerv[ing his] career toward a search for the connections between mathematics and the experience of the Logos".