This dataset provides concentration-response data and associated general chemistry conditions for 32 experiments consisting of 177 toxicity tests regarding the acute toxicity of individual major ion salts and binary mixtures of major ions to Ceriodaphnia dubia; it also provides LC50 estimates and the estimated chemistries at the LC50 for each toxicity test. This dataset is associated with the following publication: Erickson, R., D. Mount, T. Highland, J. Hockett, D. Hoff, C. Jenson, T. Norberg-King, and B. Forsman. Acute Toxicity of Major Geochemical Ions to Fathead Minnows (Pimephales promelas). ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY. Society of Environmental Toxicology and Chemistry, Pensacola, FL, USA, n/a - n/a, (2022).