The Chlorophyte algae (which means green plants) are one of the most diverse plant phyla, although their number of species (over 5000) is not comparable to that of flowering plants. They have a worldwide distribution and inhabit environments ranging from the driest deserts to the perpetual snows of Antarctica, with their greatest diversity in the tropics.

They are aquatic or occasionally terrestrial organisms, photosynthetic or, with few exceptions, parasitic. They can be unicellular or multicellular, but with cells that are not highly specialized. Sometimes they can be several centimeters in size but consisting of a single cell. They contain chlorophyll a and b and store starch in their plastids. Their life cycles are varied, with some species having cycles similar to those of animals, while others require several generations to complete the cycle. They generally have both haploid and diploid phases, although the duration of each is highly variable.

Chlorophyte algae play a very important role in aquatic ecosystems, as they form the base of the food chain for many organisms. They are a very ancient group, fully developed even before the appearance of animals.