William Sidney Porter House, Historic house museum in Downtown Austin, United States.

The William Sidney Porter House is a small wooden cottage in downtown Austin, Texas, built in 1886 as a simplified version of the Eastlake style. It has decorative wooden trim and was moved around the block to Brush Square Park at 409 East 5th Street in 1934. The house is now the O. Henry Museum, with rooms furnished with period pieces, including some of Porter's furniture and personal belongings.

Built in 1886 as a simplified Eastlake-style cottage, the house was rented by William Sydney Porter from 1893 to 1895, where he lived with his wife Athol and daughter Margaret before the family moved to Houston and he wrote full-time for the Houston Post. In 1930 it was slated for demolition to make way for a warehouse; women's heritage organizations proposed moving it, and the City of Austin relocated it to Brush Square Park, restoring it as a museum in 1934. It joined the National Register of Historic Places on June 18, 1973.

The museum displays period pieces, including some of the Porter family's own furniture and belongings. It is also the site of the annual O. Henry Pun-Off, a spoken pun competition held the first weekend in May.

The house is open to the public and welcomes visitors to explore the rooms and learn about the period through the objects on display. Wear comfortable shoes since you will walk through multiple rooms with period details that reward careful observation.

Each year on the first weekend in May, Brush Square Park hosts the O. Henry Pun-Off, a spoken pun competition held at the museum. In 1999 the site became the first National Literary Landmark in Texas, designated by the Center for the Book at the Library of Congress.