Eighteen new ingol-type diterpenes, euphorantins A-R (1-18), along with four known analogues (19-22), were isolated from the aerial parts of Euphorbia antiquorum. Compounds 1-3 are the first examples of C-17-oxygenated ingol-type diterpenes, and compounds 16-18 represent a rare class of 2,3-di-epimers of ingols. Diterpenes 1, 14, and 22 exhibited inhibitory activities against mouse 11β-HSD1 with IC50 values of 12.0, 6.4, and 0.41 μM, respectively.