On the television series The X-Files (1993–2002) episodes could be generally placed in one of two categories:

• "Mytharc" episodes were recognized as the "mythology" of the series canon; these episodes comprised the central storyline, which developed from one season to the next, concerning extraterrestrial life on Earth and a long-term conspiracy to hide the extraterrestrial presence and deal with its implications.
• Monster of the Week (MOTW or MoW) came to denote the remainder of the X-Files episodes. Episodes of this type, comprising the majority of the series' episodes, dealt with a wide range of paranormal phenomena, including cryptids and mutants; science fiction technologies; horror monsters; and satiric/comedic elements. MOTW were usually standalone episodes, but some of these episodes had indirect ties to the X-Files mythology. A number of "monster of the week" characters became notable and were later referenced by other episodes.