Cortinarius caesiocolor is a species of fungus in the large mushroom genus Cortinarius (subgenus Phlegmacium). Found in southern Finland, where it grows with oak, poplar, and hazel in deciduous forests, roadsides, and parks, it was described as new to science in 2014. The specific epithet refers to the bluish-violet color of the cap. C. chromataphilus is a sister species.