Hanna is a town in Carbon County, Wyoming, United States. The population was 683 at the 2020 census. The town was started as a coal supply location for the Union Pacific Railroad. Much of the old town is built on top of the former workings of the Hanna No. 4 mine. On December 18, 1979, the Town of Hanna annexed the adjacent Town of Elmo. The population peaked at 2,288 in 1980 and has declined as local coal mines have ceased operation.