A new lanthanum bismuth oxyhydroxide, La0.26Bi0.74OOH was prepared by a low temperature hydrothermal reaction. The oxyhydroxide crystallized in the orthorhombic system with the lattice parameters a = 3.808(1), b = 3.811(1) and c = 8.600(3) angstrom, space group Pmm2, and Z = 2. The crystal structure was determined by single crystal X-ray analysis with the final R factors being R = 0.046 and Rw = 0.057 for 240 unique reflections. The structure may be regarded as the PbFCl structure type with the first example of complete substitution of OH on the Cl site. This is also the first complete structure determination of compound having a PbFCl structure which is distorted from the usual tetragonal symmetry.