A file folder (or simply folder) is a kind of folder that holds papers together for organization and protection. File folders usually consist of a sheet of heavy paper stock or other thin, but stiff, material which is folded in half, and are used to keep paper documents. Files may also contain other things like magazines, cased in music CDs, etc. sometimes mostly not used for any official use, rather used as normal storage in a home. They are often used in conjunction with a filing cabinet for storage. File folders can easily be purchased at office supply stores.

File folders are usually labeled based on what is inside them. Folders can be labeled directly on the tab with a pen or pencil. Others write on adhesive labels that are placed on the tabs. There are also electronic label makers that can be used to make the labels.

File folders can be made from plastic or paper. When paper is used, it is preferable that it is made from paper pulp with long cellulose fibre, such as kraft paper or manila paper.

File folders are a core organizational tool of bureaucracy, business administration and scientific management. The medical profession, in particular, make heavy use of file folders for individual patient records, usually collated ready to hand in rows of filing shelves of filing cabinets in alphabetical order, and continues to do so in many practices despite the ongoing migration toward electronic health records. File folders are also prevalent in the filing systems of the legal profession.

Elimination of paper records, and the file folders used to organize these is a goal of the paperless office. Document imaging through document capture software remains a finicky, labor-intensive process and in many circumstances is not yet cost effective compared to traditional paper-based filing systems, especially for archival materials; archival records often end up boxed in Bankers Boxes packed with file folders in secure storage facilities, with a retrieval latency of hours to days.