Photolysis (193 nm) of propiolic acid (HCCCOOH) was studied with Fourier transform infrared spectroscopy in noble-gas (Ar, Kr, and Xe) solid matrixes. The photolysis products were assigned using ab initio quantum chemistry calculations. The novel higher-energy conformer of propiolic acid was efficiently formed upon UV irradiation, and it decayed back to the ground-state conformer on a time scale of similar to 10 min by tunneling of the hydrogen atom through the torsional energy barrier. In addition, the photolysis produced a number of matrix-isolated 1:1 molecular complexes such as (HCCHCO2)-C-..., (HCCOHCO)-C-..., and (H2OC3O)-C-.... The (HCCHCO2)-C-... complex dominated among the photolysis products, and the computations suggested a parallel geometry of this complex characterized by an interaction energy of -9.6 kJ/mol. The (HCCOHCO)-C-... complex also formed efficiently, but its concentration was strongly limited by its light-induced decomposition. In this complex, the most probable geometry was found to feature the interaction of carbon monoxide with the OH group via the carbon atom, and the computational interaction energy was determined to be -18.3 kJ/mol. The formation of the strong (H2OC3O)-C-... complex (interaction energy -21 kJ/mol) was less efficient, which might be due to the inefficiency of the involved radical reaction.