Southwest Ledge Light is an active lighthouse marking the main entrance channel to the harbor of New Haven, Connecticut.

Completed in 1877, it was one of the first to be built on a cylindrical iron foundation, an innovation by Maj. George H. Elliot to address shifting ice that is regarded to be very important in lighthouse design.

[5][6] The Southwest Ledge Light is located at the southwestern end of a breakwater on the eastern side of the main channel into New Haven Harbor.

The structure is octagonal in shape, with an open balcony and railing around its main level, supported by large metal brackets.

The original house remained at the exposition until its close, and was then used for the Ship John Shoal Light in Delaware Bay.