Solution-processed In2O3 thin-film transistors (TFTs) were fabricated by a spin-coating process using a metal halide precursor, InCl3, dissolved in acetonitrile. A thin and uniform film can be controlled and formed by adding ethylene glycol. The synthesized In2O3 thin films were annealed at various temperatures ranging from 200 to 600 degrees C in air or in an O-2/O-3 atmospheric environment. The TFTs annealed at 500 degrees C under air exhibited a high field-effect mobility of 55.26 cm(2) V-1 s(-1) and an I-on/I-off current ratio of 10(7). In2O3 TFTs annealed under an O-2/O-3 atmosphere at temperatures from 200 to 300 degrees C exhibited excellent n-type transistor behaviors with field-effect mobilities of 0.85-22.14 cm(2) and V-1 s(-1) and I-on/I-off ratios of 10(5)-10(6). The annealing atmosphere of O-2/O-3 elevates solution-processed In2O3 TFTs to higher performance at lower processing temperature.