Ga2P3(H3O4)3H2O crystallizes in the monoclinic P2_1 space group. The structure is three-dimensional and consists of two water molecules and one Ga2P3(H3O4)3 framework. In the Ga2P3(H3O4)3 framework, there are two inequivalent Ga3+ sites. In the first Ga3+ site, Ga3+ is bonded to six O2- atoms to form GaO6 octahedra that share corners with five PHO3 tetrahedra. There are a spread of Ga–O bond distances ranging from 1.96–2.05 Å. In the second Ga3+ site, Ga3+ is bonded to six O2- atoms to form GaO6 octahedra that share corners with four PHO3 tetrahedra. There are a spread of Ga–O bond distances ranging from 1.94–2.11 Å. There are three inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to one H+0.45+ and three O2- atoms to form distorted PHO3 tetrahedra that share corners with three GaO6 octahedra. The corner-sharing octahedra tilt angles range from 46–51°. The P–H bond length is 1.40 Å. There is two shorter (1.54 Å) and one longer (1.55 Å) P–O bond length. In the second P5+ site, P5+ is bonded to one H+0.45+ and three O2- atoms to form distorted PHO3 tetrahedra that share corners with three GaO6 octahedra. The corner-sharing octahedra tilt angles range from 39–49°. The P–H bond length is 1.41 Å. There are a spread of P–O bond distances ranging from 1.53–1.55 Å. In the third P5+ site, P5+ is bonded to one H+0.45+ and three O2- atoms to form distorted PHO3 tetrahedra that share corners with three GaO6 octahedra. The corner-sharing octahedra tilt angles range from 36–41°. The P–H bond length is 1.41 Å. There is two shorter (1.53 Å) and one longer (1.54 Å) P–O bond length. There are nine inequivalent H+0.45+ sites. In the first H+0.45+ site, H+0.45+ is bonded in a single-bond geometry to one P5+ atom. In the second H+0.45+ site, H+0.45+ is bonded in a single-bond geometry to one P5+ atom. In the third H+0.45+ site, H+0.45+ is bonded in a single-bond geometry to one P5+ atom. In the fourth H+0.45+ site, H+0.45+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. In the fifth H+0.45+ site, H+0.45+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. In the sixth H+0.45+ site, H+0.45+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the seventh H+0.45+ site, H+0.45+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. In the eighth H+0.45+ site, H+0.45+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 1.00 Å. In the ninth H+0.45+ site, H+0.45+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ga3+ and one P5+ atom. In the second O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Ga3+ and one P5+ atom. In the third O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ga3+ and one P5+ atom. In the fourth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Ga3+ and one P5+ atom. In the fifth O2- site, O2- is bonded in a bent 150 degrees geometry to one Ga3+ and one P5+ atom. In the sixth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ga3+ and two H+0.45+ atoms. In the seventh O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ga3+ and one P5+ atom. In the eighth O2- site, O2- is bonded in a 2-coordinate geometry to one Ga3+ and one P5+ atom. In the ninth O2- site, O2- is bonded in a bent 150 degrees geometry to one Ga3+ and one P5+ atom. In the tenth O2- site, O2- is bonded in a bent 120 degrees geometry to one Ga3+ and one P5+ atom. In the eleventh O2- site, O2- is bonded in a distorted water-like geometry to one Ga3+ and two H+0.45+ atoms. In the twelfth O2- site, O2- is bonded in a distorted water-like geometry to one Ga3+ and two H+0.45+ atoms.