RbH2AsO4, rubidium di-hydrogenarsenate (RDA), was synthesized by partial neutralization of an aqueous H3AsO4 solution with aqueous Rb2CO3. Its paraelectric room-temperature phase is composed of virtually regular tetra-hedral [AsO2(OH)2](-) anions and Rb(+) cations, both located on -4 positions. The [AsO2(OH)2] units are connected via O-H⋯O hydrogen bonds into a three-dimensional network, whereby the H atoms are equally disordered between the O atoms. The Rb(+) cations are located in channels running along the <100> directions and coordinated by eight O atoms located at the vertices of a snub disphenoid.