The Mesozoic and Tertiary echinoids are described from Saudi Arabia. Fifty-one species, thirty-four of them new, occur in beds ranging from the Lower Jurassic to the Miocene. Two species are present in the Lower Jurassic (Toarcian) Marrat Formation, one is new: Acrosalenia marratensis. The Middle Jurassic (Bajocian-Bathonian) middle Dhruma Formation yielded eleven species, all new: Acrosalenia arabica, Acrosalenia dhrumaensis, Heterosalenia dhrumaensis, Pseudocidaris depressa, Polycyphus arabicus, Pseudosalenia magniprocta, Farquharsonia crenulata, Leioechinus namus (type species of new genus of the family Stomechinidae), Plesiechinus altus, Bothryopneustes arabica, and Bothryopneustes dhrumaensis. Thirteen species are described from the Late Jurassic (Callovian) upper Dhruma Formation, including twelve new species: Acrosalenia bowersi, Pseudocidaris romani, Pseudocidaris raratuberculata, Hypodiadema nanituberculata, Heterosalenia brocki, Heterosalenia ornata, Leioechinus amplus, Polyc