An Arrhenius base is a substance that increases the concentration of hydroxide ions (OH⁻) in an aqueous solution. This concept was introduced by the Swedish chemist Svante Arrhenius in the late 19th century. Common examples of Arrhenius bases include sodium hydroxide (NaOH) and potassium hydroxide (KOH), which dissociate in water to release hydroxide ions. In the context of acid-base chemistry, Arrhenius bases are often contrasted with Arrhenius acids, which produce hydrogen ions (H⁺) in solution. The interaction between an Arrhenius acid and an Arrhenius base typically results in a neutralization reaction, forming water and a salt.