List of Hertfordshire boundary changes

Boundary changes affecting the English county of Hertfordshire. The county borders Buckinghamshire to the west, Bedfordshire and Cambridgeshire to the north, Essex to the east and Greater London to the south. Until 1965 it had a southern boundary with Middlesex it continues to have a boundary with Middlesex. It was the administrative Middlesex County Council that was abolished not the historic County of Middlesex. This was confirmed in 2011 by the United Kingdom Government.