The Chester County Library System (CCLS) in Chester County, Pennsylvania is a library system in southeastern Pennsylvania that was organized in 1965.

The system provides materials and information for life, work and pleasure.

The library system has its history starting in West Chester, Pennsylvania where it was once housed in a new county building on West Market Street and New Street, replacing the old Chester County Prison situated in the same location only 3 years earlier in 1959.

The county building was dedicated to honor Congressman Paul Dague in 1971.

In 1982, the library in Exton received a National Association of Counties Award for its Library Literacy Program, the first in the U.S. state of Pennsylvania handling 30,000 illiterate and 15,000 non-English speaking residents.