The unprecedented heptavanadate cluster has been isolated from reactions between trisalkoxide ligands and vanadate in water at pH = 2 as a series of alkylammonium [H x V 7 O 18 (H 2 O)((OCH 2 ) 3 CR)] (4–x)- salts ( 1 – 3 , R = CH 2 OH; 4 , R = CH 3 ). Their structures have been determined and the partial stability of 4 in water assessed by a combination of multinuclear NMR spectroscopy and ESI-MS. The heptavanadate unit reported herein could represent an intermediate species in the formation of decavanadate that is blocked by attachment of tripodal ligands.