Astroviruses are one of the leading causes of viral gastroenteritis in the young, elderly, and immunocompromised. Although the prevalence is unknown, they are also thought to be associated with food- and waterborne outbreaks of acute diarrhea. This chapter will introduce readers to astroviruses, including the extensive diversity in humans; summarize what is known about food- and waterborne outbreaks; and conclude with where the field needs to go to better understand this important virus in food safety.