A large class of (0,2) Calabi-Yau σ-models and Landau-Ginzburg orbifolds are shown to arise as different “phases” of supersymmetric gauge theories. We find a phenomenon in the Landau-Ginzburg phase which may enable one to understand which Calabi-Yau σ-models evade destabilization by worldsheet instantons. Examples of (0,2) LandauGinzburg vacua are analyzed in detail, and several novel features ...