In biochemistry, flavin adenine dinucleotide (FAD) is a redox cofactor, more specifically a prosthetic group, involved in several important reactions in metabolism. FAD can exist in three (or four: flavin-N(5)-oxide) different redox states, which are the quinone, semiquinone, and hydroquinone. FAD is converted between these states by accepting or donating electrons.

In biochemistry, flavin adenine dinucleotide (FAD) is a redox cofactor, more specifically a prosthetic group, involved in several important reactions in metabolism. FAD can exist in three (or four: flavin-N(5)-oxide) different redox states, which are the quinone, semiquinone, and hydroquinone. FAD is converted between these states by accepting or donating electrons.