[en] The cross sections of the ${}^{96}$Zr(n, 2n)${}^{95}$Zr, ${}^{90}$Zr(n, 2n)${}^{89}$Zr, and ${}^{90}$Zr(n, 3n)${}^{88}$Zr reactions with the average neutron energies of 13.8-31.33 MeV were measured by using the activation and an off-line γ-ray spectrometric technique. The cross sections for the ${}^{96}$Zr(n, 2n)${}^{95}$Zr reaction at the average neutron energies of 18.91 MeV and 25.81 MeV, for the ${}^{90}$Zr(n, 2n)${}^{89}$Zr reaction at 28.74 MeV as well as for the ${}^{90}$Zr(n, 3n)${}^{88}$Zr reaction in the average energies of 27.37 MeV and 31.33 MeV are the first time measurements. The fast neutrons were generated by using the ${}^9$Be(p, n) reaction with the proton energies of 25-, 35- and 45-MeV from the MC-50 Cyclotron at the Korea Institute of Radiological and Medical Sciences (KIRAMS). The neutron spectra were simulated by using the computer code MCNPX 2.6., whereas the experimental neutron fluxes were monitored based on the ${}^{27}$Al(n, α)${}^{24}$Na reaction. The cross sections for the ${}^{96}$Zr(n, 2n)${}^{95}$Zr, ${}^{90}$Zr(n, 2n)${}^{89}$Zr, and ${}^{90}$Zr(n, 3n)${}^{88}$Zr reactions induced by mono-energetic neutrons were also calculated by using the TALYS 1.9 code. The present results are compared with the literature data and the theoretical values, and are found to be in good agreement.