Omniscience is the state of having all knowledge, or in other words, knowing everything. A character that is omniscient knows everything their opponent is going to do before they do it, and exactly what to do to win any fight. An omniscient character is still capable of being overpowered and losing, however. In the OBD, knowledge of other fictions is not a requirement for omniscience, so a character that knows everything about their own fictional universe is considered to be omniscient.

There is also "nigh-omniscience" where a character or entity knows almost everything about their fictional universe with the exception of a small amount of information (usually what an even more powerful character wishes to conceal from them)

Examples of omniscient characters in fiction:

- The One Above All (Marvel Comics)
- Tenchi Masaki (Tenchi Muyo!)
- Gan (The Dark Tower)
- Eru Iluvatar (Lord of the Rings)
- Lord of Nightmares (Slayers/Lost Universe)
- Man of Miracles (Image Comics)
- Akasha (Nasuverse)

See also:

- Omnipotence
- Omnipresence