Lumber (American English; timber in Australian English, British English, Hiberno-English, and New Zealand English) is wood that has been processed into beams and planks, a stage in the process of wood production.

Timber may refer to:

• Timber, a term common in the United Kingdom and Australia for unprocessed wood (the term Lumber is common in the USA and Canada)
• Timber bridge, a bridge made of wood
• "Timber!" is an exclamation that lumberjacks often shout out to warn others that a cut tree is about to fall