A Santa Claus machine is a hypothetical machine that is capable of creating any required object or structure out of any given material. It is most often referenced by futurists and science fiction writers when discussing hypothetical projects of enormous scale, such as a Dyson sphere. These types of future constructions would be too large for a civilization of average size to build itself, so they would need a series of machines to intelligently build the machine with little or no direct control.

The Santa Claus machine requires some great advances in technology to be possible, including the ability to take any collection of matter and reconfigure it into any other type of matter. It would also presumably require a high level of artificial intelligence to operate autonomously. Finally, one of its requirements on a gigantic project such as a Dyson sphere would likely be the ability to replicate itself. This would enable a single Santa Claus machine, given sufficient matter and energy, to construct a project of any size and operate indefinitely.

Many theorists have seen the obvious nightmare scenarios that accompany such a device, including machines running out of control and destroying an entire planet, a la the brooms in The Sorceror's Apprentice.