Stephen Cook is a prominent computer scientist known for his significant contributions to the field of computational complexity theory. He is best recognized for formulating the concept of NP-completeness in 1971, which helps classify problems based on their computational difficulty. His work laid the foundation for understanding which problems can be solved efficiently and which cannot. Cook received his Ph.D. from Harvard University and has held academic positions at various institutions, including University of Toronto. He has received numerous awards for his research, including the Turing Award in 1982, which is often regarded as the "Nobel Prize of Computing."