Keyesport Beach is the public swimming beach inside the Keyesport Recreation Area, a day-use park run by the U.S. Army Corps of Engineers, St. Louis District, on the west shore of Carlyle Lake. Carlyle Lake is a 26,000-acre reservoir on the Kaskaskia River and the largest man-made lake in Illinois. The beach is a strip of sand at the south edge of the village of Keyesport in Clinton County, on the upper part of the lake just north of the railroad causeway that splits the reservoir in two. It is one of the bigger beaches on the lake, second in size to Dam West Beach near the dam at the south end.

From Interstate 70, take Illinois Route 127 south about 10 miles, turn east on Clinton Road, and drive about four miles into Keyesport. From there, follow the signs to the recreation area on the south side of the village. Parking lots sit right behind the sand, so it's a short walk from the car to the water, and the Keyesport boat ramp is on the same stretch of shoreline. The park is about 50 miles east of St. Louis.

The swim area is open water on a big, wind-exposed reservoir rather than a pool, so expect murky, sediment-colored water and a soft lake bottom past the sand. Water warms up quickly in June and stays warm through August. There are no lifeguards. Corps beaches are swim at your own risk, so keep children within reach and stay inside the designated swim area, well away from the boat ramp and marina traffic next door. Carlyle Lake is known as a sailing lake because of its steady wind, and on a gusty afternoon the waves rolling into this shore can be stronger than people expect.

There is a fee. The Corps charges $5 per vehicle per day at its public beaches on Carlyle Lake, Keyesport included, and $5 per day to launch a boat at the ramp. You pay at the automated fee station. A $40 Corps annual day-use pass covers it, and so does an America the Beautiful interagency pass. The Corps has also waived day-use fees on a few observance days, such as its June birthday and Juneteenth in 2025. Day-use hours at Keyesport are 8 a.m. to 10 p.m.

The beach is seasonal. The Corps opens Carlyle Lake beaches close to Memorial Day weekend, depending on weather, and closes them in mid-September. In 2026 all public beaches on the lake, Keyesport included, closed on September 15, so swimming is out until next spring, although the rest of the day-use area stays open all year. Carlyle Lake holds back flood water for the Kaskaskia River, and its level rises after heavy rain, which can cover part of the sand or delay the opening. Call the Carlyle Lake Project Office at (618) 594-2484 before a trip early or late in the season.

Next to the beach are restrooms, a small playground and shaded picnic tables. A group picnic shelter for up to 75 people can be reserved on Recreation.gov for $30 a day from May through September, and it goes first come, first served the rest of the year. Keyesport Marina rents boats and has slips, and the recreation area has a fish cleaning station for anglers working the lake for crappie, white bass and catfish. The Carlyle Lake Visitor Center, with its fish aquarium and nature exhibits, is at Dam West on the south end of the lake, along with the dam and its walking and biking trail.