The Crystal Brook is an ephemeral stream located in the Mid North region of the Australian state of South Australia.

The stream was named in 1839 by the explorer Edward John Eyre for its clear water.

In most of its length it is normally a dry creek; it rises in the Wirrabara Forest area and is one of the major tributaries to the Broughton River, which it joins about 15 kilometres (9.3 mi) from the latter's mouth.

At Bowman Park there is a permanent spring, and this is probably the 'Crystal' water that Eyre was referring to when he named the stream.

The brook only flows for its whole length following exceptional rains or a wetter than usual winter or spring.