Dennis McKenna is an American ethnopharmacologist, research pharmacognosist, lecturer and author. He is the brother of well-known psychedelics proponent Terence McKenna and is a founding board member and the director of ethnopharmacology at the Heffter Research Institute, a non-profit organization concerned with the investigation of the potential therapeutic uses of psychedelic medicines.

McKenna received his Master’s degree in botany at the University of Hawaii in 1979. He received his doctorate in botanical sciences in 1984 from the University of British Columbia, where he wrote a dissertation entitled Monoamine oxidase inhibitors in Amazonian hallucinogenic plants: ethnobotanical, phytochemical, and pharmacological investigations. McKenna then received post-doctoral research fellowships in the Laboratory of Clinical Pharmacology, National Institute of Mental Health, and in the Department of Neurology, Stanford University School of Medicine.

McKenna’s research led to the development of natural products for Aveda Corporation as well as greater awareness of natural products and medicines. He has authored numerous scientific articles and books. He co-authored The Invisible Landscape with his brother Terence and Botanical Medicines: the Desk Reference for Major Herbal Supplements with Kenneth Jones and Kerry Hughes. McKenna spent a number of years as a senior lecturer for the Center for Spirituality and Healing, part of the Academic Health Center at the University of Minnesota, Twin Cities. He is now a senior research scientist for the Natural Health Products Research Group at the British Columbia Institute of Technology in the Vancouver area.