"If I Forget Thee, O Earth" is a short story written by Arthur C. Clarke and first published in 1951 in the magazine Future. It was subsequently published as part of a short story collection in Expedition to Earth (1953). The title is taken from Psalm 137:5—"If I forget thee, O Jerusalem"—which consists of the writer lamenting over the destruction of Jerusalem by the Babylonian army. The themes in the story exploit the anxieties prevalent at the time regarding nuclear warfare.
The work was well received. Christian Science Monitor reviewer Peter J. Henniker-Heaton wrote: "I do not know of any short story that has moved me more than Arthur C. Clarke's 'If I Forget Thee, Oh Earth'."