The current article is a review of the most important, accessible, and relevant literature published between April 2018 and March 2019 on the gut microbiota and inflammatory bowel disease (IBD). The major areas of publications during the time period were in the areas of human clinical studies as well as mechanistic insights from colitis models. Most papers focused on the bacterial component of the gut microbiota although some papers described aspects of the virome and mycobiome. Paediatric IBD focussed studies are the focus of a separate review within this series and are therefore not included here. Over 86 relevant papers were published in the reporting period.