Cairanoolithus is an oogenus of dinosaur egg which is found in Southwestern Europe. The eggs are large (15–19 centimetres or 5.9–7.5 inches in diameter) and spherical. Their outer surface is either smooth, or covered with a subdued pattern of ridges interspersed with pits and grooves. Multiple fossil egg clutches are known but the nest structure is unclear. The parent of Cairanoolithus is probably some kind of non-ornithopod ornithischian, possibly the nodosaurid Struthiosaurus.