The development of novel ingestible sensors can aid physicians and patients in obtaining precise data on the health status of the gut at a local level. This in turn can facilitate earlier and more accurate disease diagnosis, improve the delivery of point-of-care medicine, and allow monitoring of the gastrointestinal (GI) tract status. This Tutorial overviews characteristics of the gut for inexpert readers and reviews emerging chemical sensing technologies for the GI tract from an analytical chemistry viewpoint.