Amine oxide deoxygenation is an important process for the synthesis of nitrogenous aromatic compounds and deprotection of amine compounds; however, precious metals, organic solvents, and undesirable hydrogen sources are required. The deoxygenation of pyridine N-oxide (PyNO) over a noble metal-free titanium dioxide (TiO2) photocatalyst in water containing oxalic acid as the hydrogen source at room temperature and the stoichiometric reaction of PyNO and oxalic acid to form pyridine (Py) and CO2 with a high apparent quantum efficiency (41.5% at 320 nm) are described in this paper. In the production of Py, the effects of various parameters (commercial TiO2 photocatalysts, amounts of oxalic acid, pH of the reaction mixture, and PyNO concentration), reusability of TiO2, and applicability to various amine oxides were investigated. Adsorption experiments were also carried out, and it was revealed that the amount of PyNO adsorbed on the TiO2 surface controls the reaction rate and that an acidic condition is important for this reaction to increase the amount of PyNO adsorbed. It was shown that oxalic acid had two important functions: a hydrogen source and an acid to keep the reaction mixture acidic. High chemoselectivity was observed in the deoxygenation of amine oxides; that is, amine oxides having reducible functional groups such as chlorine and carboxyl groups and an aromatic ring were converted to the corresponding amines. PyNO in a relatively high concentration (0.1 mol dm(-3)) was almost quantitatively reduced to Py within 1 h.