D-Glucose (C6H12O6), also known as dextrose monohydrate , dextrose, or grape sugar) is a simple sugar (monosaccharide) and an important carbohydrate in biology. Cells use it as a source of energy and a metabolic intermediate. D-Glucose is one of the main products of photosynthesis and starts cellular respiration.

D-Glucose exists in several different structures, but all of these structures can be divided into two families of mirror-images (stereoisomers). Only one set of these isomers exists in nature, those derived from the "right-handed form" of Glucose, denoted D-Glucose. D-Glucose is often referred to as dextrose monohydrate. The term D-Glucose is derived from dextrorotatory glucose. Solutions of D-Glucose rotate polarized light to the right. Starch and cellulose are polymers derived from the dehydration of D-Glucose. The other stereoisomer, called L-glucose, is hardly found in nature.

In industry, D-Glucose is used as a precursor to make vitamin C in the Reichstein process, to make citric acid, gluconic acid, bio-ethanol, polylactic acid, sorbitol.