In science fiction, ultrawaves (or hyperwaves or subwaves) are transmissions or signals that may propagate faster than light through either normal space, or alternate space, such as hyperspace or subspace.
Ultrawaves are also sometimes a form of energy transmission or weapon such as a beam weapon or death-ray.
- In E. E. Smith's Lensman series, ultrawaves propagate through the sub-ether superluminally, and were used for weapons, communications, and other applications, and had various frequencies.
- In Isaac Asimov's Foundation series, "ultrawave" and "hyperwave" are used interchangeably to represent a superluminal communications medium.
- In the Star Trek universe, subspace carries faster-than-light communication (subspace radio) and travel (warp drive).
- In the Star Trek universe, the first example of an ultrawave is developed as an alternative means of faster-than-light travel, ostensibly to replace warp drive.
- In the XCOM universe, the hyperwave decoder allows the player to know what race, size, and mission a targeted UFO is on which suggest that the alien forces use hyperwaves to communicate.
- In the book A Fire Upon the Deep by Vernor Vinge, ultrawave is used as a method of faster-than-light travel in the Beyond, as well as a means of communication.
- The Cities in Flight series by James Blish featured both ultrawave (which propagated approximately 25% faster than light) and "Dirac" transmitters (which were instantaneous).