R. L. Griess Jr. is an American mathematician known for his contributions to group theory, particularly in the study of finite groups. He is best recognized for his work on the Griess group, a notable example of a non-abelian simple group. His research has significantly influenced the field of algebra and has applications in various areas of mathematics. Griess earned his Ph.D. from Michigan State University in 1970. Throughout his career, he has published numerous papers and collaborated with other mathematicians, enhancing the understanding of group structures and their properties. His work continues to be relevant in both theoretical and applied mathematics.