1,1'-Biphenyl-2,3,3',4'-tetra-carboxylic acid monohydrate.

In the organic molecule of the title compound, C(16)H(10)O(8)·H(2)O, the dihedral angle between the two benzene rings is 42.30 (11)°. Extensive O-H⋯O hydrogen bonding helps to stabilize the crystal structure.