A laser-diode-pumped Yb-doped double-clad fiber laser operating in a hybrid Q-switched regime has been demonstrated. With pulsed pump light and stimulated Brillouin scattering of the gain fiber as the Q-switching mechanisms, the laser generated nanosecond pulses with a stable repetition rate. A single-pulse energy of as much as 143.1 microJ with a peak power of 28.6 kW was obtained. Use of an external-cavity diffraction grating in the Littman configuration permitted tuning of the laser wavelength over a 15.7-THz range from 1080 to 1140 nm, and a linewidth of 0.04 nm over the whole tuning range was achieved.