Anna Jean Ayres (July 18, 1920 – December 16, 1988) was an American occupational therapist, educational psychologist and advocate for individuals with special needs. She became known for her work on sensory integration (SI) theory.

Born on a walnut farm in Visalia, California, in 1920, Ayres' parents, Fletcher and Louise (Stamm) Ayres, were both school teachers. Growing up, Ayres claimed to have symptoms similar to the dysfunctions she would later study. Ayres received her B.A. in occupational therapy in 1945, her M.A. in occupational therapy in 1954, and her PhD in educational psychology in 1961, all from the University of Southern California in Los Angeles. She began her post-doctoral work in the UCLA Brain Research Institute from 1964 to 1966 under Arthur Parmelee. She was also a faculty member in the occupational therapy and special education departments at the University of Southern California from 1955 to 1984.

Ayres wrote two books and more than thirty journal articles. In 1975 she standardized tests originally known as the Southern California Sensory Integration Tests and later revised the Sensory Integration and Praxis Tests in 1989.

In 1976, Ayres founded a private pediatric practice called the Ayres Clinic in Torrance, California, where she conducted occupational therapy assessment and intervention on children and adults with a variety of disorders, including learning disabilities and autism.

Building on the work of Charles S. Sherrington and others, she began developing the theory and associated intervention techniques of sensory integration in the 1950s by examining the relationship between the brain and behavior. By the 1960s, Ayres recognized and described "hidden disabilities" or "dysfunction in sensory integrative processes" (Ayres, 1963, 1968), which she later referred to as sensory integrative dysfunction. She originated the theory to "explain the relationship between deficits in interpreting sensation from the body and the environment and difficulties with academic or motor learning." Between 1968 and 1989, Ayres used tests of sensory integrative and practical functions with children with and without learning and sensorimotor difficulties. These were originally published as "Southern California Sensory Integration Tests" (SCSIT; 1975) and later revised as "Sensory Integration and Praxis Tests (SIPT; 1989). She published numerous factor analyses of assessment findings that allowed her to identify patterns of sensory integrative dysfunction, which were later confirmed by other researchers and expanded upon (e.g. in the context of attention deficit and hyperactivity disorder).

"Sensory integration theory is used to explain why individuals behave in particular ways, plan intervention to ameliorate particular difficulties, and predict how behavior will change as a result of intervention" (p. 5). Dr Ayres defined sensory integration as "the organization of sensations for use. Our senses give us information about the physical conditions of our body and the environment around us... The brain must organize all of our sensations if a person is to move and learn and behave in a productive manner" (p. 5).

Ayres published her definition of "sensory integration" in 1972 as the neurological process that organizes sensation from one's own body and from the environment and makes it possible to use the body effectively within the environment (p. 11). In 1979, Ayres published Sensory Integration and the Child, a book to "help parents to recognize sensory integrative problems in their child, understand what is going on, and do something to help their child"

As an intervention approach, Sensory integration therapy is used as "a clinical frame of reference for the assessment and treatment of people who have functional disorders in sensory processing" (p. 325). Ayres considered sensory integration intervention "a specialty of occupational therapy" (Ayres 1979, p. 155). Thus, the assessment and intervention from a sensory integration perspective are most commonly used by occupational therapy practitioners in their treatment of children with difficulties in occupational performance and participation related to sensory integrative or sensory processing dysfunction.