  We constrain the binary parameters of the eclipsing accreting X-ray binary
IGR J17451--3022 and the nature of its donor star. The donor mass, its radius,
and the system inclination angle are computed based on the system orbital
period and eclipse duration recently reported by Bozzo et al.\ (2016). We find
that the donor is most likely a main-sequence star with the mass comprised
within the range $\sim$(0.5--$0.8){\rm M}_{\odot}$ and the radius of $\sim\!
0.7{\rm R}_{\odot}$. Assuming that the accreting compact object in IGR
J17451--3022 is a neutron star, the duration of the nearly total rectangular
eclipses yields the inclination angle of the system of $71^\circ\lesssim
i\lesssim 76^\circ$, compatible with the presence of dips in this system. We
rule out the presence of either brown or white dwarf. However, we find an
alternative possibility that the donor star in IGR J17451--3022 could be a
partially stripped giant with a very low mass, $\sim\! 0.2{\rm M}_{\odot}$.
This case requires a substantial mass loss prior to the formation of the
giant-star He core. According to that solution, the radius would be $\sim\!
0.4{\rm R}_{\odot}$, at $i\sim 80^\circ$. We additionally show that the
well-known approximate dependence of the giant-star radius exclusively on its
core mass breaks down below $\sim\!0.3{\rm M}_{\odot}$.
