Human–dinosaur coexistence

The historical and ongoing coexistence of humans and avian dinosaurs (birds) is well established and documented. The coexistence of humans and non-avian dinosaurs, however, exists only as a recurring motif in speculative fiction, owing to the fact that humans and non-avian dinosaurs have never coexisted at any point in the history of Earth.

The notion that non-avian dinosaurs and humans actually coexisted at some time in the past or still coexist in the present is a belief rooted in pseudoscience and pseudohistory, and is common among Young Earth creationists, cryptozoologists, and some other groups. This belief often contradicts the scientific understanding of the fossil record and known geological events. Supposed evidence presented for the idea that non-avian dinosaurs persisted to modern times has often been determined to have been a hoax. Some proponents have tried to identify depictions of dinosaurs among ancient artwork or descriptions of cryptids, though such identifications are often based on outdated or incorrect ideas about dinosaur biology and life appearance and often ignore the cultural/artistic context.

Scientists consider the idea that non-avian dinosaurs survived to the present day to be untenable, with known cases of so-called "living fossils" (such as coelacanths) being far from analogous to large-bodied land vertebrates. It would require unprecedented ghost lineages without fossils for tens of millions of years and sharply contrast with the relatively good fossil record of dinosaurs and other groups in the Mesozoic.