Aprepitant, sold under the brand name Emend among others, is a medication used to prevent chemotherapy-induced nausea and vomiting (CINV) and to prevent postoperative nausea and vomiting (PONV). It may be used together with ondansetron and dexamethasone. It is taken by mouth or administered by intravenous injection.

Common side effects include tiredness, loss of appetite, diarrhea, abdominal pain, hiccups, itchiness, pneumonia, and blood pressure changes. Other severe side effects may include anaphylaxis. While use in pregnancy does not appear to be harmful, such use has not been well studied. Aprepitant belongs to the class of neurokinin-1 receptor antagonists medications. It works by blocking substance P from attaching to the NK1 receptors.

Aprepitant was approved for medical use in the European Union and the United States in 2003. It is made by Merck & Co. It is on the World Health Organization's List of Essential Medicines.