Map - Hertfordshire

Hertfordshire ( or ; often abbreviated Herts) is one of the home counties in southern England. It borders Bedfordshire and Cambridgeshire to the north, Essex to the east, Greater London to the south, and Buckinghamshire to the west. For government statistical purposes, it forms part of the East of England region.

Hertfordshire covers 634.366 sqmi. It derives its name – via the name of the county town of Hertford – from a hart (stag) and a ford, as represented on the county's coat of arms and on the flag. Hertfordshire County Council is based in Hertford, once the main market town and the current county town. The largest settlement is Watford.

Since 1903 Letchworth has served as the prototype garden city; Stevenage became the first town to expand under post-war Britain's New Towns Act of 1946.

In 2013 Hertfordshire had a population of about 1,140,700, with Hemel Hempstead, Stevenage, Watford and St Albans (the county's only city) each having between 50,000 and 100,000 residents. Welwyn Garden City, Hoddesdon and Cheshunt are close behind with around 47,000 residents.

Elevations are higher in the north and west, reaching more than 800 ft in the Chilterns near Tring. The county centres on the headwaters and upper valleys of the rivers Lea and the Colne; both flow south, and each is accompanied by a canal. Hertfordshire's undeveloped land is mainly agricultural, with much of it protected by green-belt policies. Services have become the largest sector of the county's economy. Hertfordshire is well served with motorways and railways for access to London, the Midlands and the North.

See the List of places in Hertfordshire and also List of settlements in Hertfordshire by population articles for extensive lists of local places and districts.

The county's landmarks span many centuries, ranging from the Six Hills in Stevenage built by local inhabitants during the Roman period, to Leavesden Film Studios. The volume of intact medieval and Tudor buildings surpasses London, in places in well-preserved conservation areas, especially in St Albans, which includes remains of the Roman town of Verulamium.

In 913, Hertfordshire was the area assigned to a fortress constructed at Hertford under the rule of Edward the Elder. Hertford is derived from the Anglo-Saxon heort ford, meaning deer crossing (of a watercourse). The name Hertfordshire is first recorded in the Anglo-Saxon Chronicle in 1011. Deer feature in many county emblems. Many of the names of the current settlements date back to the Anglo-Saxon period, with many featuring standard placename suffixes attributed to the Anglo-Saxons: "ford", "ton", "den", "bourn", "ley", "stead", "ing", "lett", "wood", and "worth", are represented in this county by Hertford, Royston, Harpenden, Redbourn, Cuffley, Wheathampstead, Tring, Radlett, Borehamwood and Rickmansworth.

There is evidence of human life in Hertfordshire from the Mesolithic period. It was first farmed during the Neolithic period and permanent habitation appeared at the beginning of the Bronze Age. This was followed by tribes settling in the area during the Iron Age.

Following the Roman conquest of Britain in AD 43, the Catuvellauni tribe quickly submitted and adapted to the Roman life; resulting in the development of several new towns, including Verulamium (St Albans) where in c. 293 the first recorded British martyrdom is traditionally believed to have taken place. Saint Alban, a Romano-British soldier, took the place of a Christian priest and was beheaded on Holywell Hill. His martyr's cross of a yellow saltire on a blue field is reflected in the flag and coat of arms of Hertfordshire as the yellow field to the stag or Hart representing the county. He is the Patron Saint of Hertfordshire.