Thomas Forbes "Tommy" Hartnett (born August 7, 1941) is a former American politician who served as a U.S. Representative from South Carolina.

In 1980, Hartnett won the Republican nomination for the Charleston-based 1st District after five-term incumbent Mendel Jackson Davis retired due to back problems.

He narrowly defeated his Democratic opponent, Associate Deputy Commerce Secretary Charles D. Ravenel, becoming the first Republican to win an undisputed election in the district since Reconstruction.

The district had also been trending Republican for some time at the national level; it has only supported the Democratic candidate for president once since 1956, when Jimmy Carter carried it in 1976.

Hartnett came out of retirement in 1992 to run for the United States Senate against four-term incumbent and fellow Charleston resident Ernest Hollings.