[en] The high-spin structure of ¹²¹Ba has been investigated by in-beam γ-ray spectroscopic techniques. Rotational bands based on the h_11/2, g_7/2 and tentatively d_5/2 quasineutron configurations have been established. The alignments of h_11/2 protons and neutrons are identified at ℎω_c = 0.35-0.40 MeV in the h_11/2 and g_7/2 bands whereas an alignment occurs at ℎω_c = 0.29 MeV in the (tentantively) d_5/2 band. B(M1)/B(E2) ratios were extracted and contributed to the configuration assignments. The results are interpreted within the cranked mean-field approach. (orig.)