A low-residue diet is a diet intended to reduce certain constituents of the bowel, often with consequence for functional behaviour of the bowel. It may be prescribed for patients with ailments or functional gastrointestinal disorders mitigated by fewer and smaller bowel movements each day.

The diet may be used as part of the bowel preparation before a diagnostic procedure such as colonoscopy or as a short-term therapy for acute stages of gastrointestinal illnesses such as Crohn's disease, diverticulitis, bowel obstruction, and ulcerative colitis. In addition, a low-residue diet is often prescribed before and/or after abdominal surgery or cancer treatments.

A low-fiber diet is a low-residue diet eliminating dietary fiber in particle. The terms are not always distinguished, but when they are, a low-residue diet will include additional restrictions on foods such as dairy products, which do not contain fiber but do develop residue after digestion.

If the problem lies with fermentable carbohydrates instead, the patient may be directed to a low-FODMAP diet. Some monotrophic diets, such as the carnivore diet, are implicitly low-residue, but may also sacrifice nutrition.