Eubranchus sanjuanensis is a species of sea slug or nudibranch, a marine gastropod mollusc in the family Eubranchidae.

[2] This species was described from Friday Harbour, San Juan Island, Washington.

[1] It is reported as far north as Mountain Point, Ketchikan, Alaska.

[3] It is reported to be fairly common in British Columbia, Canada in two colour forms.

[4] It has also been reported from Cobscook Bay on the Atlantic coast of North America.