Smithian may refer to:
Smithian (regional geological stage), a regional geological stage of the Early Triassic epoch (249.7 – 247.4 Ma) preceded by the Dienerian and followed by the Spathian Smithian, pertaining to, or characteristic of Adam Smith (1723–1790), Scottish philosopher and pioneer of political economy Smithian, something of, pertaining to, or characteristic of a person bearing the surname Smith