Abstract <p>To understand the role of soil algae in ecosystems, it is important to consider their spatial organization and the interactions with other representatives of soil biota. At the macroscale, soils contain not an algocenosis but rather a soil algae complex—the totality of all oxygenic photoautotrophic microorganisms inhabiting a particular soil volume during a certain time interval. Under favorable conditions, this pool forms a soil algocenosis, that is, spatially distinct surface algal growth with a characteristic taxonomic composition integrated into a unified ecosystem through allelopathic and trophic relationships. The algal complexes can be divided into the surface growth complex, the intrasoil complex, and the complex of water layer on the soil surface according to their spatial position in soil and degree of algal cell consolidation. Soil algal communities are generally much less diverse than algal communities of aquatic systems. This is caused by the specific environmental constraints acting in the soils at all taxonomic levels. Soil algae are mainly represented by Cyanobacteriota, Chlorophyta, Ochrophyta, and Charophyta. Soil algae perform key ecological functions: production of labile organic matter; atmospheric nitrogen fixation; participation in phosphorus, potassium, zinc, and iron cycling through solubilization of unavailable forms; production of allelopathic metabolites with biocidal activity for regulation of predator and pathogen populations; synthesis of phytohormones for regulation of plant physiological processes; secretion of extracellular polysaccharides for soil particle aggregation, moisture retention, and nutrient adsorption; and mechanical binding of soil particles by filamentous thalli of algae. Thus, these properties make the soil algal complex a valuable tool for enhancing soil fertility and bioremediation.</p>