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. They are often used in conjunction with a filing cabinet for storage. File folders can easily be purchased at office supplies stores.

File folders are usually labelled 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 organisational 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 organise these, is a goal of the paperless office. Document imaging through document capture software remains a labour-intensive process for archival materials; archival records often end up boxed in Bankers Boxes packed with file folders in secure storage facilities, with a retrieval time of hours to days.

File or folder are other terms used for file folders, but file folders is a common name for the item in the United States. Manila folders are likely the most common, but file folders come in many different forms. In the United States, letter and legal sizes are common.

The exact way to refer to this kind of folder which is somewhat unclear. There is no internationally standard term. The term file folder seems to be one that dominates North American language, but does not seem as common in other countries. As stated, some refer to file folders simply as folders, but in North America, this is confusing because folder can refer to several different things. Others use the term manila folders, but this is confusing because not all file folders are made of Manila hemp. This type of folder is sometimes incorrectly referred to as a "vanilla folder."

Another commonly used folder type is the hanging folder, which has hooks on all four corners that slide over a rail. Normally, hanging folders are used to file one or more manila folders, and it is not a common practice to put loose sheets directly into hanging folders. When some documents need to be retrieved, the corresponding manila folder(s) are removed from the hanging folder. The hanging folder itself is left in its place on the rails.