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.
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.
Apart from a number of minor exchanges of land with surrounding counties, the alterations in Hertfordshire's boundaries involved the following: