Laser radiation has been used to cool matter ranging from dilute gases to micromechanical oscillators. In Doppler cooling of gases, the translational energy of atoms is lowered through interaction with a laser field. Recently, cooling of a high-density gas through collisional redistribution of radiation has been demonstrated. In laser cooling of solids, heat is removed through the annihilation of lattice vibrations in the process of anti-Stokes fluorescence. Since its initial observation in 1995, research has led to achieving a temperature of 208 K in ytterbium-doped glass. In this Letter, we report laser cooling of ytterbium-doped LiYF4 crystal to a temperature of ∼155 K starting from ambient, with a cooling power of 90 mW. This is achieved by making use of the Stark manifold resonance in a crystalline host, and demonstrates the lowest temperature achieved to date without the use of cryogens or mechanical refrigeration. Optical refrigeration has entered the cryogenic regime, surpassing the performance of multi-stage Peltier coolers.