Guanosine diphosphate, abbreviated GDP, is a nucleoside diphosphate. It is an ester of pyrophosphoric acid with the nucleoside guanosine. GDP consists of a pyrophosphate group, a pentose sugar ribose, and the nucleobase guanine.

GDP is the product of GTP dephosphorylation by GTPases, e.g., the G-proteins that are involved in signal transduction.

GDP is converted into GTP with the help of pyruvate kinase and phosphoenolpyruvate.