Out of Time's Abyss is a science fantasy novel by American writer Edgar Rice Burroughs, the third of his Caspak trilogy. The sequence was first published in Blue Book Magazine as a three-part serial in the issues for August (vol. 27 #4), October (vol. 27 #6), and December (vol. 28 #2) 1918, with Out of Time's Abyss forming the third installment. The complete trilogy was later combined for publication in book form under the title of The Land That Time Forgot (the title of the first part) by A. C. McClurg in June 1924. Beginning with the Ace Books editions of the 1960s, the three segments have usually been issued as separate short novels.