The library rooms at the Guildhall contain an extensive collection of original material relating to the City of London. Amongst the very considerable holdings are parish registers, livery company apprenticeships and freedoms, wills, marriage licences, the Lloyds Marine archive, rate books, and trade & street directories.

In addition the Guildhall Library itself contains a huge collection of printed books and serials, covering not only London, but the entire British Isles.