Kelly's Directory (or more formally, the Kelly's, Post Office and Harrod & Co Directory) was a trade directory in the United Kingdom that listed all businesses and tradespeople in a particular city or town, as well as a general directory of postal addresses of local gentry, landowners, charities, and other facilities. In effect, it was a Victorian version of today's Yellow Pages. Many reference libraries still keep their copies of these directories, which are now an important source for historical research.
The eponymous originator of the directory was Frederic Festus Kelly. In 1835 or 1836 he became chief inspector of letter-carriers for the inland or general post office, and took over publication of the Post Office London Directory, whose copyright was in private hands despite its semi-official association with the post office, and which Kelly had to purchase from the widow of his predecessor.
He founded Kelly & Co. and he and various family members gradually expanded the company over the next several decades, producing directories for an increasing number of UK counties and buying out or putting out of business various competing publishers of directories.
Other publications followed, including the Handbook to the Titled, Landed and Official Classes (1875) and Merchants, Manufacturers and Shippers (1877). In 1897, Kelly & Co Ltd became Kelly’s Directories Ltd. This name stuck for another 106 years before being renamed Kellysearch in 2003 to reflect its focus away from hard copy directories and towards an Internet based product search engine.
The front cover of a Kelly's Directory sometimes stated "Kelly's Directories Ltd., established 1799", however this was based on the date of issue of the first Post Office London Directory by an earlier inspector of letter carriers several decades before Kelly's involvement with that publication.
Today, Kelly's exists online as Kellysearch, a directory similar to the online Yellow Pages. Kellysearch.com was established in Boston in 2004. It is now in many different languages and in the last few years has introduced a fully searchable online-catalogue library and product press release section.
The old editions of the Kelly’s Directories are seen as highly collectable by many and have also become a useful reference tool for people tracing the history of local areas (with the ancient data now available to buy on CD Rom from many entrepreneurial sources for this purpose.) Every edition of the Kelly’s Directory ever published is held in the Guildhall Library  in London.
- "Cottingham History". accessed 11 July 2010.
- Pendred, John (1955). "Appendix H: General Directories". In Pollard, Graham. The Earliest Directory of the Book Trade (reprint of 1785 ed.). pp. 83–84. ISBN 0-19-721759-1. "The first directories of counties outside London were published by Kelly in 1845; and during the next sixteen years the series was extended throughout England. In 1892 Kelly's Directories Ltd. acquired the majority of shares in Isaac Slater Ltd. [...]; and the firm of William White of Sheffield [...] was absorbed in 1898."
- The London Gazette: . 23 July 1897.
- "Trade Directories". Stella & Rose's Books. Retrieved 2011-03-28.
- Jane Elizabeth Norton (1966). "The Post Office London Directory". The Library (The Transactions of the Bibliographical Society). 5th series 21 (4): 293–299. doi:10.1093/library/s5-XXI.4.293. "The Post Office London Directory was started by two inspectors of the Inland letter-carriers called Ferguson and Sparkes… A third inspector, called B. Critchett, joined the enterprise in 1803 and later it was carried on by Critchett alone, then by Critchett and Woods, and then again by Critchett alone until his death in 1835. [sic; he died 18 September 1836]"
- Trade directories and telephone books at Guildhall Library
- Historical Directories has extensive online versions of old editions for England and Wales
- Forebears has transcriptions of one edition for each county
- Norton, Jane Elizabeth (1966). "The Post Office London Directory". The Library (The Transactions of the Bibliographical Society). 5th series 21 (4): 293–299. doi:10.1093/library/s5-XXI.4.293.
- Atkins, Peter J. (May 1989). "The Compilation and Reliability of London Directories". The London Journal (Maney Publishing) 14 (1): 17–28. ISSN 0305-8034.
- Jane Elizabeth Norton (1950). Guide to the national and provincial directories of England and Wales, excluding London, published before 1856 (1984 reprint ed.). Offices of the Royal Historical Society. ISBN 0-86193-102-5. (original edition: ISBN 0-901050-15-6)
- A. V. Williams (1913). The development and growth of city directories. Williams directory co.
- Pendred, John (1955). "Appendix H: General Directories". In Pollard, Graham. The Earliest Directory of the Book Trade (reprint of 1785 ed.). pp. 83–84. ISBN 0-19-721759-1.
- Peter J. Atkins (1990). The directories of London, 1677-1977. Cassell and Mansell. ISBN 0-7201-2063-2.