Single-walled carbon nanotubes were assembled into large-area arrays of nanoscale rings on silicon via direct patterning with a self-assembled colloidal polystyrene sphere mask. Nanotubes from liquid suspension gathered at the base of each sphere in the mask to form rings, and the resulting arrays consisted of well-ordered nanotube rings with diameters of 203 +/- 21 nm and 97 +/- 14 nm for rings formed with 780 and 450 nm colloidal spheres, respectively. Ring heights were found to be 4.7 +/- 1.8 nm and 5.9 +/- 1.4 nm for 780 and 450 nm sphere masks, respectively. A first-order geometric model was proposed to account for the observed ring diameters. The approach presented demonstrates an efficient and straightforward path for patterning carbon nanotubes into well-defined surface distributions on various substrates with highly controlled and tunable dimensions.