The Forel-Ule scale is a method to estimate the color of bodies of water. The scale provides a visual estimate of the color of a body of water, and it is used in limnology and oceanography with the aim of measuring the water's transparency and classifying its biological activity, dissolved substances, and suspended sediments.

François-Alphonse Forel was a Swiss physician and scientist who pioneered the study of lakes, and is thus considered the founder, and the Father of limnology. Limnology is the study of bodies of fresh water and their biological, chemical, and physical features.