Dennis Jon McKenna (born in 1950, Colorado, USA) is an ethnopharmacologist, researcher, and writer recognized for his pioneering work in the scientific study of visionary plants and for his commitment to bridging ancestral knowledge with modern science. For over four decades, he has devoted his life to exploring the relationship between humans, sacred plants, and consciousness.

Trained in biology and botany, he earned his Ph.D. from the University of British Columbia, where he researched ayahuasca and other Amazonian preparations. He has worked at institutions such as the National Institute of Mental Health and Stanford University, and is a founding Board member of the Heffter Research Institute, an organization dedicated to the scientific study of psychedelics in therapeutic and ritual contexts. From 2001 to 2017, he taught courses in ethnopharmacology and plants in human affairs in the Center for Spirituality and Healing in the Academic Health Center at the University of Minnesota.

McKenna was also one of the principal investigators of the Hoasca Project, the first biomedical study on ayahuasca use within the União do Vegetal community in Brazil. Since 2019, he has led the McKenna Academy of Natural Philosophy, a 501(3)c nonprofit dedicated to dialogue between science, philosophy, and ancestral wisdom, promoting a renewed relationship between humanity and nature. The Academy organized and presented two landmark conferences on the Ethnopharmacologic Search for Psychoactive Drugs; ESPD50 in 2017 and ESPD55 in 2022. Ben de Loenen, Director of ICEERS, was collaborating editor of the symposium proceedings for both events.

Author of numerous scientific articles and books —including The Brotherhood of the Screaming Abyss, where he recounts his life alongside his brother Terence McKenna— Dennis is regarded as a key figure in the contemporary resurgence of psychedelic studies. His work unites academic rigor, spiritual insight, and deep respect for the Indigenous traditions that have safeguarded the knowledge of sacred plants.