O Moon (1990) is a lithograph on black paper by Nancy Holt, produced in an edition of 16. Made at the San Antonio Art Institute in Texas, it  is one of only two lithographs she created. While the moon is a recurring point of reference in Holt’s interest in light, celestial phenomena, and visual perception, O Moon is a rare work in which she represents the moon directly as an image.

In 1972, Holt created Moon Book, a collaged fourteen-page book that brings together disparate relationships and perceptions of the moon across a wide span of time. One page includes an image sourced from an advertisement for the Questar telescope in the July 1967 issue of Sky & Telescope magazine; Holt returns to this image in O Moon.