Three new species of Cryptantha from the Channel Islands of southern California are described. Cryptantha clementina, endemic to San Clemente Island, was formerly identified as C. traskiae I.M.Johnst. It is distinct from that species in having a low, spreading growth habit, congested inflorescence cymules, wider corolla limbs, thicker and more swollen midrib calyx trichomes, and nutlets that are tuberculate throughout the dorsal and ventral surfaces. Cryptantha kinkiensis, also endemic to San Clemente Island, was previously identified as C. intermedia (A.Gray) Greene. It differs from that species in having bifurcate cymules and nutlets with denser, smaller tubercles. Cryptantha catalinensis, endemic to Santa Catalina Island, was previously identified as either C. intermedia or C. wigginsii I.M.Johnst. It differs from C. intermedia in having bifurcate cymules and nutlets with denser, smaller nutlet tubercles. It differs from C. wigginsii in having nutlets that are tuberculate apically and low-tuberculate to glabrate basally, as opposed to densely tuberculate apically (tubercles “wart-like” and generally abutted) and glabrous and shiny basally in C. wigginsii. Cryptantha catalinensis and C. kinkiensis are somewhat similar to one another, but distinct in nutlet sculpturing and midrib calyx trichome size. We note morphological similarities and some evidence for phylogenetic relatedness among Cryptantha clementina, C. traskiae, and C. foliosa (Greene) Greene, the last endemic to Guadalupe Island, Baja California, Mexico. We also point out morphological similarities among Cryptantha catalinensis, C. kinkiensis, and C. wigginsii. Detailed molecular phylogenetic studies are needed to evaluate the evolutionary and biogeographic history of these new insular species.