We report here the first examples of metal-metal quadruple bonds supported by calixarene ligands in the complexes [Mo 2 (OAc) 2 (H 2 -calix[4]arene)] (1) and [Mo 2 (OAc) 2 (H 2 -p-tert-butylcalix[4]arene)] (2). Complexes 1 and 2 were prepared by first deprotonating calix[4]arene and p-tert-butyl-calix[4]arene, respectively, with two equivalents of KH, followed by the addition of [Mo 2 (OAc) 2 (NCMe) 6 ][BF 4 ] 2 . X-ray crystallographic analysis revealed the solid state structure of 2(THF) C 6 H 6 . A molybdenum-molybdenum quadruple bond (2.1263(6) ) is spanned by two bridging acetate ligands and a tetradentate, doubly-deprotonated calixarene macrocycle. Each Mo-Mo unit is weakly coordinated by an axial THF solvent molecule which is included in the calixarene basket of the neighboring complex.