A wěi tuō shū (letter of authorization) is a formal written document that grants one person or organization the legal authority to act on behalf of another. The three characters combine meaningfully: wěi means 'to entrust' or 'to appoint', tuō means 'to entrust' or 'to delegate' (reinforcing the idea), and shū means 'document' or 'letter'. Together, they literally mean 'a document of entrustment'.

This term is commonly used in administrative, legal, and business contexts — for example, when someone authorizes another to collect official documents, sign contracts, or represent them at government offices. It is more formal and legally specific than casual phrases like ràng...bāngmáng ('ask someone to help'). A wěi tuō shū typically includes names of both parties, scope of authority, duration, and signatures — often requiring notarization for official use.