Jonathan David Haidt (/haɪt/; born October 19, 1963) is an American social psychologist and author. He is the Thomas Cooley Professor of Ethical Leadership at the New York University Stern School of Business. Haidt's main areas of study are the psychology of morality and moral emotions.

Haidt's main scientific contributions come from the psychological field of moral foundations theory, which attempts to explain the evolutionary origins of human moral reasoning on the basis of innate, gut feelings rather than logic and reason. The theory was later extended to explain the different moral reasoning and how they relate to political ideology, with different political orientations prioritizing different sets of morals. The research served as a foundation for future books on various topics.

Haidt has written multiple books for general audiences, including The Happiness Hypothesis (2006) examining the relationship between ancient philosophies and modern science, The Righteous Mind (2012) on moral politics, and The Coddling of the American Mind (2018) on rising political polarization, mental health, and college culture. In 2024, he published The Anxious Generation, arguing that the rise of smartphones and overprotective parenting has led to a "rewiring" of childhood and increased mental illness.

Haidt was born to a secular Jewish family and was raised in Scarsdale, New York. His grandparents were Russian and Polish natives who immigrated as teenagers to the United States, where they became garment workers. Haidt described his upbringing as "very assimilated", identifying as an atheist by age 15. His father, an Ashkenazi Jew, was a corporate lawyer. The family generally were New Deal liberals.

At age 17, Haidt recalled that he experienced an existential crisis upon reading Waiting for Godot and existential literature. After attending Scarsdale High School, he was educated at Yale University, graduating magna cum laude in 1985 with a Bachelor of Arts in philosophy, then briefly held a job as a computer programmer before pursuing graduate studies in psychology at the University of Pennsylvania, where he received a Master of Arts and PhD in the field in 1988 and 1992, respectively, on a graduate fellowship awarded by the National Science Foundation. His dissertation was titled "Moral judgment, affect, and culture, or, is it wrong to eat your dog?" and was supervised by psychologists Jonathan Baron and Alan Fiske. Inspired by anthropologist Paul Rozin, Haidt wrote his thesis on the morality of harmless but disgusting acts.

From July 1992 to June 1994, Haidt was an NIMH postdoctoral fellow at the University of Chicago, where he studied cultural psychology under the supervision of cultural anthropologist Richard Shweder. Haidt called Shweder "the teacher that most affected me". At Shweder's suggestion, Haidt researched moral complexity in Bhubaneswar, India, where he conducted field studies and "encountered a society in some ways patriarchal, sexist and illiberal". From July 1994 to August 1995, he was a postdoctoral associate with the MacArthur Foundation under psychologist Judith Rodin.

In August 1995, Haidt became an assistant professor at the University of Virginia (UVA), where he was eventually named an associate professor in August 2001, then a full professor of the university's psychology department in August 2009. He remained at Virginia until 2011, winning four awards for teaching, including a statewide award conferred by Governor Mark Warner. Haidt also earned a reputation for challenging the general assumptions in moral psychology. His research, centered on the emotional origins of morality with particular focus on the emotions of disgust and elevation, led to the publication of The Happiness Hypothesis in 2006.

In 1999, Haidt became active in the new field of positive psychology, studying positive moral emotions. This work led to the publication of an edited volume, Flourishing, in 2003. In 2004, Haidt began to apply moral psychology to the study of politics, doing research on the psychological foundations of ideology. This work led to the publication in 2012 of The Righteous Mind. Haidt spent the 2007–2008 academic year at Princeton University as the Visiting Professor for Distinguished Teaching. In July 2010, he delivered a talk at the Edge Foundation on the new advances in moral psychology.