Abstract: Drilling fluids, methods, and systems for drilling a subterranean formation. Drilling fluids include an aqueous base fluid and a shale inhibitor comprising cetyltrimethylammonium bromide. Methods include providing the drilling fluid and drilling at least a portion of a wellbore into a subterranean formation in the presence of the drilling fluid. Systems include a drill string extendable into the wellbore from a drilling platform and conveying the drilling fluid to a drill bit arranged at a distal end of the drill string. The subterranean formation may be a shale subterranean formation.