Olanzapine (trade name Zyprexa or in combination with fluoxetine Symbyax) is an atypical antipsychotic, approved by the FDA for the treatment of schizophrenia and bipolar disorder. Olanzapine is structurally similar to clozapine, but is classified as a thienobenzodiazepine. The olanzapine formulations are manufactured and marketed by the pharmaceutical company Eli Lilly and Company; the drug went generic in 2011. Sales of Zyprexa in 2008 were $2.2B in the US alone, and $4.7B in total.

Known FDA approvals are as follows:

Case-reports, open-label, and small pilot studies suggest efficacy of olanzapine for the treatment of some anxiety spectrum disorders (e.g. generalized anxiety disorder,panic disorder,delusional parasitosis,post-traumatic stress disorder); however, olanzapine has not been rigorously evaluated in randomized, placebo-controlled trials for this use and is not FDA approved for these indications. Other common off-label uses of olanzapine include the treatment of eating disorders (e.g. anorexia nervosa) and as an adjunctive treatment for major depressive disorder without psychotic features. It has also been used for Tourette syndrome and stuttering.