Marble Falls is a city in Burnet County, Texas, United States. As of the 2020 United States Census, the city population was 7,037. The 2024 population was estimated to be 9,413. Lake Marble Falls is part of the Highland Lakes on the Colorado River, the largest chain of lakes in Texas. Marble Falls was founded by Adam Rankin Johnson in 1887, a former Indian fighter and Confederate general.