The Cape Sebastian Sandstone is a Mesozoic geologic formation in the state of Oregon in the United States. Hadrosaurid dinosaur remains, such as the sacrum of the Cape Sebastian ornithopod (described in 2019), are among the fossils that have been recovered from the formation, although none have yet been referred to a specific genus. The formation dates to the Campanian stage of the Late Cretaceous epoch.^{[1] [2][3]}

Cape Sebastian Sandstone
Stratigraphic range: Campanian, 83.6–72.1 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Type	Geological formation
Location
Region	Oregon