Thomas Berry Brazelton (May 10, 1918 – March 13, 2018) was an American pediatrician, author, and the developer of the Neonatal Behavioral Assessment Scale (NBAS). Brazelton hosted the cable television program What Every Baby Knows, and wrote a syndicated newspaper column. He wrote more than two hundred scholarly papers and twenty-four books.

Brazelton was born in Waco, Texas. He studied at the Episcopal High School in Alexandria, Virginia.

He graduated in 1940 from Princeton University and in 1943 from the Columbia University College of Physicians and Surgeons in New York City, where he accepted a medical internship at Roosevelt Hospital. From 1945, after war service in the U.S. Navy, he completed his medical residency in Boston Massachusetts General Hospital (MGH) before undertaking pediatric training at Children's Hospital of Boston.

He entered private practice in 1950, in Cambridge, Massachusetts. His interest in child development led to training in child psychiatry at MGH and the James Jackson Putnam Children's Center. He subsequently served as a Fellow with Professor Jerome Bruner at the Center for Cognitive Studies at Harvard University, then combined his interests in primary care pediatrics and child psychiatry and in 1972 established the Child Development Unit, a pediatric training and research center at Children's Hospital in Boston. From 1988, he was Clinical Professor of Pediatrics Emeritus at Harvard Medical School.

Brazelton was president of the Society for Research in Child Development (1987–1989), and of the National Center for Clinical Infant Programs (1988–1991). He appeared many times before Congressional committees in support of parental and medical leave bills, and continued to work with the Alliance for Better Child Care for a more comprehensive day care bill. He was a co-founder of Parent Action and served on the National Commission on Children.

Brazelton is widely known for developing a "child-oriented" approach suggesting to start toilet training not earlier than 24 months of child's age while looking for "readiness signs" for mature toilet behavior. In his work, he shared his opinion that "...there is little innate in the child that leads [them] to want to be clean and dry, it must be understood as a kind of compliance to external pressure", that parents should withstand "external pressure" of grandparents to start toilet education around 9 months of age and postpone it until a child is demonstrating certain "readiness signs". Later Brazelton served as Chairman of Pampers Parenting Institute funded by P&G Corporation, a global disposable diaper market leader. He also participated in Pampers advertising for Toddler diapers N6.

Brazelton appeared several times on The Oprah Winfrey Show and the Ellen DeGeneres Show. Brazleton was the paediatrician of television and podcast personality Conan O'Brien in the 1960s–70s.

Brazelton's foremost achievement in pediatrics and child development has been to increase pediatricians' awareness of, and attention to, the effect of young children's behavior, activity states, and emotional expressions on the ways their parents react to, and thereby affect them. For example, one of his first publications in the field of psychology was a study with Kenneth Kaye of the interaction between babies' sucking at breast or bottle and the mother's attempts to maintain it, the earliest form of human "dialogue". The Brazelton Neonatal Behavioral Assessment Scale (NBAS) assesses not only the physical and neurological responses of newborns, but also their emotional well-being and individual differences.