The scientific principle stating that mass cannot be created or destroyed is known as the law of conservation of mass. This fundamental concept, established in the 18th century by Antoine Lavoisier, asserts that the mass of an isolated system remains constant over time, meaning that the total mass of reactants in a chemical reaction will equal the total mass of the products. This principle is essential in chemistry and various scientific fields, as it underpins the understanding of chemical reactions and the conservation of matter.