The rational control of superconductivity and the possibility of deterministically enhancing the superconducting transition temperature (T_c) by design, rather than by serendipity, has been an elusive and long sought-after goal in solid-state physics. Here, we report the first instance of transmuting a normal metal into a superconductor through the application of epitaxial strain. We demonstrate that synthesizing RuO₂ thin films on TiO₂(110) substrates stabilizes superconductivity under strain, having T_cs up to 2 K; by contrast, RuO₂ thin films grown on TiO₂(101) substrates are non-superconducting down to the lowest measured temperatures (T_c < 0.4 K), consistent with the behavior of bulk RuO₂. Using a comprehensive combination of characterization techniques—including electrical transport, x-ray diffraction, scanning transmission electron microscopy, angle-resolved photoemission spectroscopy, and density functional theory—we reveal the primary electronic mechanism underlying this strain-stabilized superconductivity: the anisotropic strains redistribute the carriers amongst the manifold of 4d states near the Fermi level (E_F), partially depopulating flat bands with d_|| orbital character, and thereby increase the density of states at E_F.