Highly infrared transparent tetragonal ZrO2 (3 mol% yttria-stabilized) was prepared by means of high-pressure spark plasma sintering (HP-SPS). The crystallite size of the resulting dense sample was about 80 nm. In-line transmittance for the 1.5 mm thick sample ranged between 63% and 67% in the wavelength of 3-5 mu m, representing 81%-87% of the theoretic value. Meanwhile, the cutoff wavelength of tetragonal ZrO2 was superior to the values of other high-strength transparent ceramics. This study highlighted the efficiency and simplicity of HP-SPS for obtaining transparent tetragonal ZrO2 and the great potential of this ceramic applied for durable infrared windows.