Marble Falls is a city in Burnet County, Texas, United States. The population was 4,959 at the 2000 census. Marble Falls is 45 minutes west of Austin and 85 miles north of San Antonio. Lake Marble Falls is part of the Highland Lakes, the largest chain of lakes in Texas. According to the United States Census Bureau, the city has a total area of 17.4 km˛ (6.7 mi˛). 15.9 km˛ (6.1 mi˛) of it is land and 1.4 km˛ (0.6 mi˛) of it (8.21%) is water.

As of the census of 2000, there were 4,959 people, 1,931 households, and 1,266 families residing in the city. The population density was 311.8/km˛ (807.1/mi˛). There were 2,085 housing units at an average density of 131.1/km˛ (339.3/mi˛). The racial makeup of the city was 85.80% White, 2.48% African American, 0.40% Native American, 0.42% Asian, 0.02% Pacific Islander, 8.87% from other races, and 2.00% from two or more races. Hispanic or Latino of any race were 22.54% of the population. There were 1,931 households out of which 35.1% had children under the age of 18 living with them, 47.1% were married couples living together, 14.3% had a female householder with no husband present, and 34.4% were non-families. 29.8% of all households were made up of individuals and 13.2% had someone living alone who was 65 years of age or older. The average household size was 2.51 and the average family size was 3.10.