Glucose (C₆H₁₂O₆) is a simple carbohydrate, or sugar. It is one of several kinds of sugars. It is important because cells in an organism use it as a source of energy. Turning glucose into energy is called cellular respiration, which is done inside the cells of a living organism. Excess glucose is converted to fats and are stored in adipose tissues.

Glucose is made by plants in a process called photosynthesis. It can also be made by animals in their liver or kidneys.