The title compound, lithium trimanganese bis[trioxoselenate(IV)] hexakis[hydrogentrioxoselenate(IV)], is built up from a vertex-sharing network of distorted MnIII
pyramids, and unusual Li(OH)6
octahedra, resulting in a dense three-dimensional structure. Mn, Li and one Se atom have site symmetries of
, and 3, respectively. An O—H⋯O hydrogen bond helps to establish the crystal packing.