3-(2-Ethyl-2-phenyl-hydrazin-1-yl-idene)indolin-2-one.

In the title compound, C16H15N3O, the dihedral angle between the indole ring system (r.m.s. deviation = 0.020 Å) and the phenyl ring is 14.49 (9)°. The mol-ecular conformation is supported by an intra-molecular C-H⋯O inter-action, which closes an S(7) ring. In the crystal, inversion dimers linked by pairs of N-H⋯O hydrogen bonds generate R2(2)(8) loops.