This article critically reviews the current availability and selected use of genetic technologies for horses, before undertaking an ethical evaluation of current practice and regulatory positions in comparative relation to debates surrounding genetic testing, preimplantation genetic testing and gene editing in humans. We argue that genetic testing for hereditary disorders is not only justified but should be encouraged on welfare grounds and that genetic testing for performance traits is ethically permissible based on a restricted imperative to genetically edit horses and horse embryos to reduce genetic predisposition to disease and injury. Given the current state of the science, where the effects of gene editing on health and welfare are currently undetermined, space is created for an analytical distinction between equine gene editing for 'treatment' and for 'enhancement'. Gene editing is only justified for purposes of correcting/preventing disease and injury. Current regulation is challenged by apparently conflicting welfare-based ethical imperatives with respect to welfare-based gene editing. We propose modifications to the blanket bans on gene editing with a case-by-case assessment of applications to permit gene editing, based on best welfare interests underwritten by the aim of facilitating fair sport that adapt WADAs International Standard for Therapeutic Use Exemptions, adding an important reporting element. We reject the use of gene editing to obtain currently prohibited competitive advantages. In order to safeguard the welfare of human and equine athletes, we argue that regulatory institutions should urgently collaborate to develop cross-sport international regulations for the use of gene editing, including obligatory reporting of data about the health and welfare of genetically edited horses.