Williams and Stancliff Octagon Houses

The Joseph Williams Octagon House and the Gilbert Stancliff Octagon House are once-identical historic mid-1850s octagon houses located next to each other at 26 and 28 Marlborough Street in Portland, Connecticut. Constructed of Portland brownstone, their architect is unknown but may have been Gilbert Stancliff's brother Charles. Their architectural style has been described as Octagon Mode and Italianate.

The pair of houses, also known as the Octagon House Pair, was added to the National Register of Historic Places in 1976.