One of the most pernicious 1 and long-standing problems in density functional theory (DFT) is that of selfinteraction error (SIE), which arises due to incomplete cancellation of Hartree self-repulsion by approximate exchange-correlation (XC) functionals. SIE manifests as overstabilization of fractionally-charged systems, leading to underestimation of barrier heights and motivating the use of hybrid functionals. When generalized gradient approximations (GGAs) are used to describe openshell systems, the result is over-delocalization of unpaired spins. Conventional hybrid functionals with 20-25% exact exchange do not always fully eliminate this delocalization error. Of particular interest in the present work are polaron defects in transition metal and maingroup oxides, where the extent of defect delocalization is sensitive to the fraction of exact exchange. We demonstrate that density-corrected (DC-)DFT can be used both to detect and to correct over-delocalization of polaron defects. DC-DFT is a simple procedure whereby a selfconsistent Hartree-Fock (HF) density (ρ HF ) is used to evaluate the XC energy via a single Roothaan step: E xc [ρ HF ]. This procedure incorporates electron correlation effects but avoids self-consistent iterations at the DFT level, which would introduce SIE into the density. This approach has been shown to afford reasonable reaction barrier heights even when GGA functionals are used for E xc . Although the basic idea is quite old, it has been revived and championed by Burke, Sim, and coworkers, and more recently by others, as an ad hoc correction for problems where delocalization error is "density-driven" rather than "functional-driven". In such cases, errors are often ameliorated through the use of a SIE-free density, ρ HF . The usefulness of DC-DFT therefore hinges on identifying cases where the error that are density-driven. Where the errors are instead functional-driven, it is probably not advantageous to sacrifice self-consistency.