Thomas A. Cahill (1828-1878) was an entrepreneur and philanthropist who bequeathed the bulk of his estate to establish the Roman Catholic High School for the Boys, the first free Catholic high school in the United States.

Located in Philadelphia, the school was founded in 1890 and initiated a diocesan high school system that became a model throughout the nation. Coming from a poor immigrant family, Cahill sought to provide young men from similar backgrounds with the secondary education he was denied.