Dylath-Leen is a fictional city in H. P. Lovecraft's Dream Cycle and appears in The Dream-Quest of Unknown Kadath (1926) and Brian Lumley's short story Dylath-Leen.
It is built mostly of basalt, and its streets are both dark and uninviting. It is one of the most mysterious cities in Lovecraft's Dreamlands. The citizens buy rubies from strange, turbaned men in sinister black galleys (whose rowers are never seen), though the famous dreamer Randolph Carter has advised against this practice. In the Lumley story this plot-line is continued, with a new dreamer discovering that the moon-beasts have finally taken over the city, despite Carter's warnings.