5-Nitro-1-n-octyl-1H-benzimidazol-2(3H)-one.

The benzimidazolone part of the mol-ecule of the title compound, C(15)H(21)N(3)O(3), is almost planar (r.m.s. deviation = 0.007 Å) with its mean plane aligned at a dihedral angle of 10.4 (3)° with respect to the mean plane of the nitro substituent. In the crystal, two mol-ecules are disposed about a center of inversion, generating an N-H⋯O hydrogen-bonded cyclic dimer with R(2) (2)(8) graph-set motif.