A lumber mill is an industrial facility where unrefined sections of wood (tree trunks and branches) are sawed into usable forms of wood, usually boards or sheets. It does not include pulp mills or paper mills, where trees are chopped into very fine bits.

The operation saws raw sections of wood into usable forms. The product can be a board or sheet while retaining the material as cut wood.

Reducing wood to fine particles or pulp is a different process. Wood shredding and paper mills cover those outputs.