The 236U(nth, f) cross section was measured for the first time at the high-flux reactor of the Institut Laue-Langevin in Grenoble, yielding a value of (0.3 ± 1.0) mb. This means that f 1.3 mb, which is about two orders of magnitude lower than previously adopted. This result was obtained by combining a highly enriched 236U sample with a very clean neutron beam and assuming that the Westcott factor gf = 1 for 236U(n, f) with cold neutrons. The new value is compatible with the latest fission resonance data and with the subthreshold character of the thermal neutron induced fission of 236U.