Reissner's membrane (vestibular membrane, vestibular wall) is a membrane inside the cochlea of the inner ear. It separates scala media from scala vestibuli. Together with the basilar membrane it creates a compartment in the cochlea filled with endolymph, which is important for the function of the organ of Corti. It primarily functions as a diffusion barrier, allowing nutrients to travel from the perilymph to the endolymph of the membranous labyrinth.