Robert Bruce Merrifield is an American biochemist.

He was born in Fort Worth, Texas, 15 July, 1921, the only son of George E. Merrifield and Lorene née Lucas. In 1923 the family moved to California where he attended nine grade schools and two high schools before graduating from Montebello High School in 1939. It was there that he developed an interest both in chemistry and in astronomy.

After two years at Pasadena Junior College he transferred to the University of California at Los Angeles (UCLA). After graduation in chemistry he worked for a year at the Philip R. Park Research Foundation taking care of an animal colony and assisting with growth experiments on synthetic amino acid diets. One of these was the experiment by Geiger that first demonstrated that the essential amino acids must be present simultaneously for growth to occur.

He returned to graduate school at the UCLA chemistry department with professor of biochemistry M.S. Dunn to develop microbiological methods for the quantitation of the pyrimidines. The day after graduating on 19 June, 1949, he married Elizabeth Furlong and the next day left for New York City and the Rockefeller Institute for Medical Research.

At the Institute, later Rockefeller University, he worked as an Assistant for Dr. D.W. Woolley on a dinucleotide growth factor he discovered in graduate school and on peptide growth factors that Woolley had discovered earlier. These studies led to the need for peptide synthesis and, eventually, to the idea for solid phase peptide synthesis in 1959. He has received many awards for this work, including the Nobel Prize in 1984.

After raising six children, his wife, a biologist by training, joined the Merrifield laboratory at Rockefeller University.