A novel 1 kHz single-frequency Q-switched Er:YAG laser pumped by a 1470 nm laser diode (LD) is demonstrated. The 500 ns, 5.52 mJ single-frequency diffraction-limited pulses are obtained by using a ‘Ramp-fire’ injection-seeding technique and an optical feedback architecture. The half-width of the pulse spectrum is measured to be 1.47 MHz by using the heterodyne technique. The beam quality M2 factors are measured to be 1.18 and 1.24 in x and y directions, respectively.