The single-crystal structure of the title compound {systematic name: poly[tetraaquatri-μ2-sulfato-diholmium(III)]}, [Ho2(SO4)3(H2O)4]n, features two-dimensional holmium(III) sulfate layers constructed by eight-coordinate holmium and sulfate groups. The coordination about Ho includes four O atoms from bridging sulfate ions. One S atom makes three S—O—Ho linkages through bridging O atoms, while a second S atom lies on a twofold axis and makes two S—O—Ho linkages. The coordination of each Ho atom is completed by four water molecules, which act as terminal ligands of Ho3+.