Hulda Regehr Clark (18 October 1928 in Rosthern, Saskatchewan – 3 September 2009 in Chula Vista, California) was a Canadian naturopath, author, and practitioner of alternative medicine. Clark claimed all human disease was related to parasitic infection, and also claimed to be able to cure all diseases, including cancer and HIV/AIDS, by "zapping" them with electrical devices which she marketed. Clark wrote several books describing her methods and operated clinics in the United States. Following a string of lawsuits and eventual action by the Federal Trade Commission, she relocated to Tijuana, Mexico, where she ran the Century Nutrition clinic.

Clark's claims and devices have been dismissed by authorities, ranging from the United States Federal Trade Commission and Food and Drug Administration to CAM figures such as Andrew Weil, as scientifically unfounded, "bizarre", and potentially fraudulent. Clark died 3 September 2009 from blood and bone cancer.