A term applied to the style of certain works of Greek sculpture in the period ca. 480-450 BCE. The Severe Style can be understood as transitional between the Archaic and Classical styles. Characteristics include simplicity of forms (in contrast to the more decorative forms of Archaic sculpture) and serious facial expressions. The term came into general use with Vagn Poulsen’s 1937 study Der strenge Stil (“The Severe Style”). Web resource here.
East metope 4 from the Temple of Zeus at Olympia, Greece: an example of Severe Style sculpture. Parian marble. 470–457 BCE. Archaeological Museum of Olympia. Photo: Egisto Sani.