Stephen Southmyd Fenn (born March 28, 1820) was a Democratic politician who represented the Idaho Territory in the United States Congress during the late nineteenth century. Serving as a territorial delegate rather than a voting member from a numbered congressional district, he is recorded as representing Idaho’s at-large district, listed here as district “-1,” reflecting the territory-wide nature of his constituency.

Fenn held the role of Representative from December 6, 1875, to March 3, 1879, completing two terms in office. During this period, he served as Idaho’s voice in the House of Representatives, participating in congressional deliberations on behalf of the territory. Although specific committee assignments, legislative initiatives, and additional offices are not documented in the available metadata, his tenure places him among the early political figures who helped shape Idaho’s path in the years before statehood.