Reptilians in this context, also commonly known as "lizard people", are a theorized race of shapeshifting aliens, the idea of which was conceptualized in 1888 but popularized by conspiracy theorist David Icke in 1998. Among other things, the theory claims that they are trying to subjugate humanity, usually by either hybridizing with humans or impersonating people in positions of power.

There is no commonly-accepted "canonical" appearance for them, with depictions—both among people who believe the theory‚ and in speculative fiction—ranging from anthro to humanoid, so this tag is for when there are other contextual indicators that this is the intent.

See also: Reptilian conspiracy theory on Wikipedia
For reptilians in general, see: Scalie, Reptile