Deborah Pierson Delmer is an American plant pathologist, and professor emeritus at University of California, Davis. She was one of the first scientists to discover the enzymes and biochemical mechanisms for tryptophan synthesis. Delmer became president of the American Society of Plant Biologists (ASPB) as of 1999. Delmer was awarded the 2011 ASPB Leadership in Science Public Service Award and the 2003 Anselme Payen Award.