Oviposition-site choice is a major maternal effect by which females can affect the survival and phenotype of their offspring. Across oviparous species, the ultimate reasons for females' selection of oviposition sites often differ. We present six hypotheses that have been used to explain nonrandom oviposition-site choice in insects, fish, amphibians, reptiles, and birds: (a) maximizing embryo survival, (b) maximizing maternal survival, (c) modifying offspring phenotype, (d) proximity to suitable habitat for offspring, (e) maintaining natal philopatry, and (f) indirect oviposition-site choice via mate choice. Because these hypotheses differ in their relevance across oviparous taxa, each hypothesis must be tested to ensure accurate understanding of the ultimate reason behind oviposition-site choice in a particular taxon. By presenting the major hypotheses for oviposition-site choice as they relate to diverse oviparous animals, we nonetheless illustrate particular trends across animal taxa, while highlighting avenues for future research into the ecological and evolutionary drivers of oviposition-site choice.