The National Maritime Museum was established by the National Maritime Museum Act 1934, supplemented by the National Maritime Museum Act 1989 and the Museums and Galleries Act 1992. Its charitable purposes are set out in section 3 of the 1934 Act and section 1 of the 1989 Act.

For legal purposes, the National Maritime Museum entity incorporates the Royal Observatory, the Peter Harrison Planetarium, the Queen’s House the Cutty Sark and the Prince Philip Maritime Collection Centre. Royal Museums Greenwich (RMG) is a collective brand name for the sites.

The National Maritime Museum is a non-departmental public body (NDPB), operating at arm's length from government, but accountable to Parliament. It is an exempt charity whose Principal Regulator is the Secretary of State for Culture, Media and Sport.

The Framework Document sets out the broad governance framework within which RMG and the DCMS operate:

https://www.gov.uk/government/publications/the-royal-museums-greenwich-framework-document-2025-to-2028