A forest fire retardant composition contains a retardant compound that includes a phosphate salt. The phosphate salt may include diammonium phosphate, diammonium orthophosphate, monoammonium phosphate, monoammonium orthophosphate, monosodium phosphate, disodium phosphate, disodium phosphate hydrate, sodium ammonium phosphate, sodium ammonium phosphate hydrate, sodium tripolyphosphate, trisodium phosphate, or dipotassium phosphate, and combinations thereof. The forest fire retardant composition may include an ammonium source. The composition may be in the form of a dry concentrate, a liquid concentrate, or a final diluted product. The final diluted product is effective in suppressing, retarding, and controlling forest fires while exhibiting corrosion resistance and low toxicity.