David Menhennet CB (4 December 1928 - 5 February 2016) was a British librarian. As librarian at the House of Commons Library from 1976 to 1991, he oversaw a period of modernisation and other improvements to the library, transforming the library into a modern research facility.
Menhennet was born in Redruth, Cornwall, the son of William and Everill Menhennet. He attended Truro School on a scholarship and excelled in languages, going on to graduate with a first in French and German from Oriel College, Oxford. He then moved to Queen's College to study for a D.Phil in 18th century French literature.
He became a clerk in the Commons Library in 1954. When given responsibility for the research area in 1964 he introduced a system of comprehensive daily briefings for MPs, and he was promoted to Deputy Librarian in 1967. When Speaker George Thomas appointed him 10th Librarian of the Commons Library in 1976, he began a process of modernisation. He set up the Public Information Office (now the House of Commons Information Office) in 1978, and electronic publication began the same year, when the Library contributed to the Prestel viewdata system, which at one time had 90,000 subscribers. Computerisation of the Library's information systems began in 1979 with the creation of the Parliamentary On-Line Information System (POLIS). He also established a service for schools. The new systems introduced by Menhennet enabled MPs to find and check information far more easily, and were used particularly often by Gordon Brown and Tony Blair while in opposition.
Menhennet hosted international conferences at Westminster, and also acted as an adviser to other parliaments. His last reform was to ban smoking in the library.