Theodore Lidz (1 April 1910 – 16 February 2001) was an American psychiatrist best known for his articles and books on the causes of schizophrenia and on psychotherapy with patients with schizophrenia. An advocate of research into environmental causes of mental illness, Lidz was a notable critic of what he saw as a disproportionate focus on biological psychiatry. Lidz was a Sterling Professor of Psychiatry at Yale University. In his lifetime, he did a great amount of research on interpersonal causes of schizophrenia.