Rax is a mountain range in the Northern Limestone Alps on the border of the Austrian federal provinces of Lower Austria and Styria.
RAX or Rax may also refer to:
- Gallius Rax, character from the Star Wars: Aftermath trilogy of science fiction novels
- Hello Summer, Goodbye (Rax in the US), a science fiction novel by British author Michael G. Coney
- Radio Aurora Explorer, the first National Science Foundation sponsored CubeSat mission
- RAX, a 64-bit register in the x86 family of instruction set architectures
- IBM Remote Access Computing, called RAX, an obsolete System/360 time-sharing system
- Rax Roast Beef, a regional U.S. fast food restaurant chain
- RAX-2, a CubeSat satellite built as a collaboration between SRI International and students at the University of Michigan
- Retinal homeobox protein Rx, a protein that in humans is encoded by the RAX gene
- Ragnar Axelsson, a photographer