This review is the first in a series of three articles considering how different types of dietary fibre may affect how the gut functions and gut health. This first review will focus on the impact of dietary fibre intake on the upper gastrointestinal tract (i.e. the mouth, oesophagus and stomach). While a larger body of evidence links fibre intake to bowel health and disease, it is apparent that the presence of fibre, whether as an added ingredient in foods, or as an integral part of the structure of plant foods, also plays key roles on oral and gastric secretions and upper gut motility. These actions are possibly modulated through fibre's effects on the physicochemical properties of luminal contents in the gut. The major physiological functions of the mouth, oesophagus and stomach are discussed and recent evidence relating dietary fibre intake to these actions is introduced. A summary of evidence linking habitual dietary fibre consumption to major mucosal diseases of the upper gastrointestinal tract is also provided.