Charophyceae is a taxon of green algae whose exact rank is the matter of some current debate. Some botanists recommend expanding the existing plant kingdom to include charophyceans and chlorophytes while others consider Charophyceae to be a class within either the divisions Chlorophyta, Streptophytina, or Streptophyta. Other systematists classify Charophyceae as a class under division Charophyta, with Chlorophyta remaining a distinct division.

Regardless of the exact classification of charophyceans, the consensus among botanists is that they are the organisms most closely related to embryophytes (traditional plants). Many of the complex traits related to sexual reproduction, photosynthesis, and other defining characteristics of plants evolved first in charophyceans; analysis of cpDNA (chloroplast DNA), for instance, reveals that many characteristics of plant chloroplasts evolved first in the charophycean genera Staurastrum and Zygnema.

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