Olanzapine (originally branded Zyprexa) is an atypical antipsychotic. It is approved by the U.S. Food and Drug Administration (FDA) for the treatment of schizophrenia and bipolar disorder.

Olanzapine is structurally similar to clozapine and quetiapine. It is a dopamine antagonist and 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, and $4.7B worldwide.