We report the first demonstration of a UV laser using a high-Q whispering gallery mode (WGM) resonator of Ce<sup>3+</sup>: LiCaAlF<sub>6</sub>. We show that WGM resonators from LiCaAlF<sub>6</sub> can achieve a Q of 2.6 x 10<sup>7</sup> at UV. We demonstrated a UV laser at 290 nm with a pulsed pump laser at 266 nm. The experiments showed the low pump threshold intensity of 7.5 x 10<sup>9</sup> W/m<sup>2</sup> and slope efficiency of 25%. We have also observed lasing delay dynamics. These results are consistent with our modeling and theoretical estimates, and pave the way for a low threshold cw UV laser using WGM resonator cavity.