A compact passively Q-switched Yb:YAG microchip laser is demonstrated. Featuring a semiconductor saturable-absorber mirror (SESAM), the laser yields pulses of 219 ps when the length of the microchip Yb:YAG crystal is 100 μm and the beam quality is M2<1.3. To the best of our knowledge, pulses from the proposed laser are the shortest Q-switching pulses obtained from Yb:YAG microchip lasers currently available.