This paper predicts the first realization of topological crystalline insulators in the semiconductor SnTe, identifying its nonzero topological index. SnTe is predicted to have metallic surface states with an even number of Dirac cones on high-symmetry crystal surfaces such as \{001\}, \{110\}, and \{111\}. These surface states form a high-mobility chiral electron gas robust against disorder and protected by reflection symmetry. Breaking this symmetry through elastic strain engineering or in-plane magnetic fields can open a tunable band gap, leading to potential applications in thermoelectrics, infrared detection, and tunable electronics. Related semiconductors PbTe and PbSe also become topological crystalline insulators under pressure, strain, or alloying. The study uses first-principles calculations and a simplified tight-binding model to analyze the electronic properties and perturbations affecting the surface states.This paper predicts the first realization of topological crystalline insulators in the semiconductor SnTe, identifying its nonzero topological index. SnTe is predicted to have metallic surface states with an even number of Dirac cones on high-symmetry crystal surfaces such as \{001\}, \{110\}, and \{111\}. These surface states form a high-mobility chiral electron gas robust against disorder and protected by reflection symmetry. Breaking this symmetry through elastic strain engineering or in-plane magnetic fields can open a tunable band gap, leading to potential applications in thermoelectrics, infrared detection, and tunable electronics. Related semiconductors PbTe and PbSe also become topological crystalline insulators under pressure, strain, or alloying. The study uses first-principles calculations and a simplified tight-binding model to analyze the electronic properties and perturbations affecting the surface states.