This work investigates stereolithography at a liquid-liquid interface. The first working curves printed at a liquid-liquid interface are presented and closely match those printed at liquid-solid interfaces. A model describing the curing behavior at a liquid-liquid interface is derived and suggests that print speeds up to 162 cm/hour are possible with a commercially available resin. Resin cure speeds of 159 cm/hr and prototype system print speeds of 81 cm/hr were demonstrated using liquid-liquid interface stereolithography. The suitability of various aqueous, organic, and fluorinated organic liquid subphases are evaluated based on UV transmission, environmental considerations, immiscibility, spreading behavior, density, and chemical compatibility with the resin. High quality single-layer prints can be produced on multiple subphases. Print quality decreases for 3D prints due to capillary effects at the interface. The trade-off between resin spreading and subphase wetting at the print interface is explored.