The structure of a nanospheric polyhydrido copper cluster, [Cu-20(H)(11){S2P((OPr)-Pr-i)(2)}(9)], was determined by single-crystal neutron diffraction. The Cu-20 cluster consists of an elongated triangular orthobicupola constructed from 18 Cu atoms that encapsulate a [Cu2H5](3-) ion with an exceptionally short Cu-Cu distance. The 11 hydrides in the cluster display three different coordination modes to the Cu atoms: six mu(3)-hydrides in a pyramidal geometry, two mu 4-hydrides in a tetrahedral cavity, and three mu(4)-hydrides in an unprecedented near square-planar geometry. The neutron data set was collected for 7 days on a small crystal with dimensions of 0.20 mm x 0.50 mm x 0.65 mm using the Spallation Neutron Source TOPAZ single-crystal time-of-flight Laue diffractometer at Oak Ridge National Laboratory. The final R-factor was 8.63% for 16,014 reflections.