The glaucophytes, also known as glaucocystophytes or glaucocystids, are a small group of rare freshwater microscopic algae. Together with the red algae (Rhodophyta)  and the green algae plus land plants (Viridiplantae or Chloroplastida), they form the Archaeplastida. However, the relationships among the red algae, green algae and glaucophytes are unclear, in large part due to limited study of the glaucophytes.