Bronsted acidity is a concept in acid-base proton theory, which indicates the ability of substances to release protons (H+).

Specifically, a substance HA, after releasing H+, becomes A-, and its Bronsted acidity is the equilibrium constant of the reaction HA = H++A-. The larger the equilibrium constant, the easier it is for HA to release protons, and the stronger its Bronsted acidity is.