Fort Zumwalt Park is an historic site within O’Fallon in St. Charles County, in the US state of Missouri. The fort dates back to the pioneer era in the early 19th century, shortly after the Louisiana Purchase, and was the fortification of the Zumwalt Family. In 1798 Jacob Zumwalt (1752–1820), a Revolutionary War veteran, settled on the spot. With the outbreak of the War of 1812 and increasing Indian problems, the Zumwalt's home was enlarged, portholes were added and the compound was enclosed within a stockade fence. It became the fortified gathering place for area settlers during times of Indian uprisings. It is said that the Zumwalt home was the first hewn-log house built on the west side of the Mississippi River. The first Methodist Sacrament in Missouri was said to have been celebrated in the Zumwalt home in 1807. The land was sold in 1837 to Major Nathan Heald. The land was purchased by the state of Missouri in the early 20th century, and became Fort Zumwalt State Park. The park was subsequently sold to the City of O'Fallon for the symbolic sum of one dollar in 1978, at which time it became a city park.

All that remains of the original Zumwalt home is an internal stone chimney with 2 fireplaces, one on either side. The site also includes the Darius Heald Home.

In 2008 the O'Fallon Community Foundation began work on the reconstruction of Zumwalt's home. On September 30, 2009, the O’Fallon Community Foundation held a ribbon cutting to celebrate the completion of the first phase of the reconstruction of Jacob Zumwalt’s homestead fort. The plan was to have all three phases of Zumwalt's log structures reconstructed by 2012 in timing with the bicentennial of the War of 1812. By the end of 2013, however, delays had put the completion time in doubt.

The park's total area is 48-acre (19 ha) with 4-acre (1.6 ha) Lake Whetsel, a picnic pavilion, a shelter house and a children's playground with equipment. The lake is open for fishing from February though October (7am–7pm). Fort Zumwalt Park also hosts O'Fallon's annual Celebration of Lights, a drive-through display of light decorations, every Christmas season.

The local Fort Zumwalt School District R-II is named after this fort.