Our in situ x-ray diffraction and Raman measurements of Yb₂Ti₂O₇ pyrochlore show that it undergoes a reversible structural phase transition from cubic pyrochlore to a monoclinic phase at ˜28.6 GPa. Analysis of the x-ray data shows the transition to be thermodynamically first order and the high pressure phase to be substitutionally disordered. These experimental results are supported by our first principles calculations.