Water desalination is an energy-intensive process needed in many parts of the world to provide fresh water for drinking, agriculture, and industry. The energy for desalination can come from conventional fossil fuels such as petroleum, natural gas, and coal, as well as renewable energy sources such as solar, wind, hydro, and geothermal. One renewable energy source that is widely available but currently unused for water desalination is biomass. The goal of this review was to understand why this is, how biomass compares to other renewable energy sources for water desalination, and under what circumstances the moveable and non-intermittent nature of biomass may provide advantages. The main limitation for biomass is cost, driven by the needed feedstock volumes and process complexity. Biomass-to-heat for thermal desalination technologies is simpler but more energy-intensive. Biomass-to-electricity for membrane desalination uses less energy but has complex processes. Biomass use will likely remain limited to small-scale capacity needs, infrastructure-poor or rural areas with few other options, brackish waters, and abundant, underutilized biomass supplies.