LEO-vetter automatically vets transit signals found in light curve data. Inspired by the Kepler Robovetter (ascl:2012.006), LEO-vetter computes vetting metrics to be compared to a series of pass-fail thresholds. If a signal passes all tests, it is considered a planet candidate (PC). If a signal fails at least one test, it may be either an astrophysical false positive (FP; e.g., eclipsing binary, nearby eclipsing signal) or false alarm (FA; e.g., systematic, stellar variability). Pass-fail thresholds can be changed to suit individual research purposes, and LEO-vetter produces vetting reports for manual inspection of signals. Flux-level vetting can be applied to any light curve dataset (such as Kepler, K2, and TESS), including light curves with mixes of cadences, while pixel-level vetting has been implemented for TESS.