Kodomo no Jikan (Japanese: こどものじかん, "A Child's Time") is a Japanese manga series written and illustrated by Kaworu Watashiya. The story revolves around a grade school teacher named Daisuke Aoki, whose main problem is that one of his students, Rin Kokonoe, has a crush on him. It was serialized between May 2005 and April 2013 in Futabasha's Comic High! magazine and is compiled in 13 volumes. At one time, an English-language version of the manga was licensed by Seven Seas Entertainment for distribution in North America under the title Nymphet, but they ultimately decided not to publish it due to controversies over its content. It was then relicensed by Digital Manga, who released the series in English through e-book.

A 12-episode anime adaptation of the series aired in Japan between October and December 2007. While content of the broadcast version was sometimes heavily censored, the DVD releases of the individual episodes remain unedited. A second anime season was released as four original video animation episodes between January and July 2009. A third original anime DVD was released in January 2011.