Hillhouse Avenue is a street in New Haven, Connecticut, famous for its many nineteenth century mansions, including the president's house at Yale University. Both Charles Dickens and Mark Twain have described it as "the most beautiful street in America." Much of the avenue is included in the Hillhouse Avenue Historic District, which extends to include houses on adjacent streets.

James Hillhouse was an American lawyer, real estate developer, and politician from New Haven, Connecticut. He represented the state in both chambers of the US Congress. From February to March 1801, Hillhouse briefly served as President pro tempore of the United States Senate.