Humans evolved with, and continue to harbor, trillions of microorganisms living inside or on our bodies. As a result, these microbes play fundamental roles in our health. The last 20 years of research has focused almost exclusively on our resident bacteria. New technologies have enabled identification of viruses within the intestine, i.e. “the virome”. Moreover, recent studies indicate that the gut virome is significantly altered in patients with IBD, and that viruses can have a protective function in mice. However, the contribution of the virome to a healthy gut and how changes in virus composition impacts gut inflammation is almost completely unknown. Here, we propose to identify components of the human intestinal virome that shape our immune system in the context of health and IBD. This work will identify protective roles for the intestinal virome – a contrast to the misconception that all viruses are harmful.