The first complete dinosaur eggs recognized by science were discovered in 1923 during an American Museum of Natural History expedition in Mongolia.
The expedition, led by Roy Chapman Andrews, was searching the Gobi Desert for early human fossils when its team encountered fossilized eggs at the Flaming Cliffs. The eggs were initially attributed to Protoceratops because that herbivorous dinosaur was abundant nearby. Later evidence showed they belonged to the theropod Oviraptor.
There is an important historical distinction: eggshell fossils had been found in southern France as early as 1859, but they were mistaken for giant bird eggs and were not recognized as dinosaur eggs. The 1923 discovery became famous because it provided convincing, recognizable evidence that dinosaurs laid eggs and preserved complete nests.
The discovery also helped launch modern research into dinosaur reproduction. Paleontologists now study eggshell structure, nests, embryos, and growth lines to investigate dinosaur behavior and incubation.