Distilled water refers to water that has undergone distillation and condensation processes. Water distilled twice is called double-distilled water, and water distilled three times is called triple-distilled water^[1]. It has low oxygen consumption. Industrial distilled water is obtained through distillation methods. This entry provides a detailed introduction to the concept of distillation, distilled water, multiple-distilled water, standards for distilled water, production methods, advantages, and uses. It also includes a comparative analysis with deionized water, high-purity water, and ultrapure water.