Noroviruses are a group of related, single-stranded RNA, non-enveloped viruses that cause acute gastroenteritis in humans. They belong to the genus Norovirus, family Caliciviridae. The most common symptoms of acute gastroenteritis include diarrhea, vomiting, and stomach pain.

Noroviruses spread from person to person, through contaminated food or water, and by touching contaminated surfaces. Norovirus is recognised as the leading cause of foodborne-disease outbreaks in the United States. Outbreaks can happen to people of all ages and in a variety of settings.

Norovirus is the official genus name for the group of viruses previously described as "Norwalk-like viruses" (NLV).