A passively Q-switched Er:YAP laser of 2.7 µm, utilizing Au-doped CsPbI₃ quantum dots (QDs) as a saturable absorber (SA), was realized. It was operated stably with a minimum pulse width of 185 ns and a maximum repetition rate of 480 kHz. The maximum pulse energy and the maximum peak power were 0.6 μJ and 2.9 W, respectively, in the Q-switched operation. The results show that the CsPbI₃ QDs SA exhibits remarkable laser modulation properties at ~3 μm.