Crestline is a census-designated place in the San Bernardino Mountains of San Bernardino County, California, USA. The population was 10,770 at the 2010 census, up from 10,218 at the 2000 census.
According to the United States Census Bureau, Crestline has a total area of 14.0 square miles (36 km sq). 13.8 square miles (36 km2) of it is land and 0.1 square miles (0.26 km sq) of it (1.00%) is water. Crestline is located within the San Bernardino National Forest; Lake Gregory is located in the center of Crestline.