Casey Creek is a major tributary of the Big Muddy River in Illinois, United States.

Like most of the rest of the Big Muddy basin, Casey Creek flows through an ancient lake bed from the Wisconsin glaciation.

Heading south, the lake bed becomes recognizable about 10 miles (16 km) north of Mt.

In the north, the flat valley bottom is only a few hundred feet wide, but it widens toward the south.

At full flood, Casey Creek rages between the two railroad embankments, which are about 3,000 feet (910 m) apart.

Vernon sewage treatment plant discharges to Casey Creek to the southeast of the city.

The Big Muddy and Casey Creek have been dammed near their confluence in Franklin County, forming Rend Lake.