Hepatitis E is an infectious viral disease with clinical and morphological features of acute hepatitis. The etiological agent is the hepatitis E virus (HEV), mainly transmitted via the fecal-oral route. The disease represents an important public health problem in developing countries, where it is often related to epidemic outbreaks mainly associated with consumption of contaminated water. In recent years, an increasing number of sporadic cases have also been described in industrialized countries. Besides humans, the virus has also been identified in animals, firstly swine in 1997, and is now considered ubiquitous. Human and swine HEV strains from the same regions present a high level of nucleotide identity, and experimental infections have confirmed the cross-species transmission of swine strains to humans and of human strains to non-human primates. Studies on anti-HEV antibodies detection have demonstrated that people working in contact with swine or wild boar have a higher risk of infection than normal blood donors. Recently, cases of hepatitis E in Japan and France were directly associated with ingestion of uncooked meat from pigs, wild boar or deer. Today the disease is considered an emerging zoonosis. This book summarizes the current virological and epidemiological knowledge on HEV infections, focusing on a virus that has not yet received enough attention in veterinary medicine, although it may become an important zoonotic agent.