Ernest I, called "Ernest the Pious" was a duke of Saxe-Gotha and Saxe-Altenburg. The duchies were later merged into Saxe-Gotha-Altenburg.

Saxe-Gotha was one of the Saxon duchies held by the Ernestine branch of the Wettin dynasty in the former Landgraviate of Thuringia. The ducal residence was erected at Gotha.