<p>Epitaxy has advanced the thin-film electronics field by enhancing many key features of semiconductors. While halide perovskites are performing well in photovoltaics, their potential for high-end electronics applications remains underexplored, and epitaxial investigations have been limited. Here we demonstrate the epitaxial growth of single-domain pseudomorphic perovskite cesium tin chloride (CsSnCl₃) on metal halide (NaCl) substrates by reactive vapor phase epitaxy. An epitaxially stabilized tetragonal perovskite phase is demonstrated via a combination of in-situ and ex-situ diffraction techniques, which differs from its non-perovskite monoclinic bulk phase. Moreover, we vary growth stoichiometries to uncover the epitaxial growth of another distinct tetragonal phase (CsSn₂Cl₅) having markedly dissimilar lattice parameters accommodated by epitaxial rotation around the NaCl substrate. The CsSnCl₃ epitaxy is also exploited to grow 2D quantum wells of CsSnCl_3, resulting in clear quantum confinement in photoluminescence where we extract the effective Bohr radius of 5.2 ± 0.9 nm. This work further extends how epitaxy can be utilized for the evolution of new halide perovskite phases to extend their potential beyond photovoltaics.</p><p></p>