The Icknield Way is generally said to be one of the oldest roads in Great Britain, being one of the few long-distance trackways to have existed before the Romans occupied the country, of which the route can still be traced. However, there are contrary views, and the evidence for its being a prehistoric route has been questioned.
How old or indeed prehistoric the way may be in its origin is much debated as indeed is what stretches of apparent ancient path can be said to belong to it. The name is said to have been used initially for the part to the west and south (south of the River Thames) but the name is given too to the track or traces north of the Thames, specifically at the top or the foot of the scarp of the Chiltern Hills.
Early documentary evidence
The earliest mentions of the Icknield Way are in Anglo-Saxon charters from the year 903 onwards. The oldest surviving copies were made in the 12th and 13th centuries, and these use the spellings Ic(c)enhilde weg, Icenhylte, Icenilde weg, Ycenilde weg and Icenhilde weg. The charters refer to locations both north and south of the Thames, at Wanborough, Wiltshire, at Hardwell in Uffington, Harwell and Blewbury in Berkshire and Risborough in Buckinghamshire, which places span a distance of 40 miles and if a single path it spans four counties.
The origin of the name of the way is unknown. There are those who champion a pre-Roman British derivation, perhaps after the famous Iceni tribe of East Anglia. A more recent origin might be with the Icelingas, the royal house which gave birth to the kings of East Anglia and Mercia, or it may be unrelated to either.
The "Four Highways" of mediæval England
The Icknield Way was one of four highways that appear in the literature of the 1130s. Henry of Huntingdon wrote that the Ermine Street, Fosse Way, Watling Street and Icknield Way had been constructed by royal authority. The Leges Edwardi Confessoris gave royal protection to travellers on these roads, and the Icknield Way was said to extend across the width of the kingdom. The mischievous myth-maker Geoffrey of Monmouth elaborated the story by saying that Belinus had improved the four roads so that it was clear that they were the protected highways.
Around 1250, the Four Highways were shown by Matthew Paris on a diagramatic map of Britain called Scema Britannie. The Icknield Way is depicted by a straight line from Salisbury to Bury St Edmunds which intersects the other three roads near Dunstable.
In the 14th century, Ranulf Higdon described a different route for the Icknield Way: from Winchester to Tynemouth by way of Birmingham, Lichfield, Derby, Chesterfield and York. This route includes the Roman road running from Bourton-on-the-Water to Templeborough near Rotherham, which is now called Icknield Street (or Ryknild Street) to distinguish it from the Icknield Way.
In many places the track consists or consisted of several routes, particularly as it passes along the line of the escarpment of the Chilterns, probably because of the seasonal usage, and possibly the amount of traffic especially of herds or flocks of livestock.
To the west the track can be detected below the escarpments of the Wessex Downs. Near Wantage in Berkshire, the route along the ridge of the Downs is known as The Ridgeway, and the name Icknield Way is applied to a parallel lowland route above the spring-line at the northern edge of the chalk.  Between Lewknor and Ivinghoe there are two parallel courses known as the Lower Icknield Way and the Upper Icknield Way. In Cambridgeshire, Street Way (Ashwell Street), Ditch Way and others have been put forward as variant routes, possibly for use in summer or winter.
Many modern roads follow the Icknield Way, for example the B489 from Aston Clinton to Dunstable and the A505 from Baldock to Royston. In some places, especially from the east of Luton in Bedfordshire to Ickleford (so named from the Way crossing a stream) near Hitchin in Hertfordshire, the route is followed by minor roads, and is not distinguishable at all in many places, except by landscape features such as barrows and mounds which line the route, and indentation presumably from ancient and frequent use. It could be described as a belt studded with archaeological sites found at irregular intervals.
The Icknield Way forms the boundary between Hertfordshire and Cambridgeshire, and as it cuts through the middle of Royston (as the A505) so Royston is divided between the two counties, Cambridgeshire to the north, Hertfordshire to the south. It is in the middle of Royston that the Icknield Way crosses Ermine Street.
In the south-west some writers take the Way as far as Exeter, while others only take it to Salisbury. To the north-east, Icklingham, Suffolk, and Caistor-by-Norwich, Great Yarmouth and Hunstanton, Norfolk have all been proposed as the destination. Speculative placig of the route through Dersingham led to the marking of a road there as “Icknield Way” on some 20th century maps.
The Hobhouse Committee report of 1947 suggested the creation of a path between Seaton Bay and the Chiltern ridge, and in 1956 Tom Stephenson proposed a longer route to Cambridge. A route through Norfolk was discussed in the 1960s. The first section to be officially designated as a Long-Distance Footpath (as National Trails were then known) was that from Overton Hill to Ivinghoe Beacon, and it was declared open as The Ridgeway in 1973. The Peddars Way from Knettishall Heath to Holme-next-the-Sea forms part of the Peddars Way and Norfolk Coast Path National Trail, which was opened as a Long Distance Route in 1986. Between the Ridgeway and Peddars Way, most of the original line of the Icknield Way had been covered in tarmac or built over, so a nearby route was devised that avoids walking on roads, and in 1992 this was designated by the Countryside Commission as a Regional Route called the Icknield Way Path. The Wessex Ridgeway from Lyme Regis to Marlborough was declared open by Dorset County Council in 1994.
The author Ray Quinlan has combined most of the Wessex Ridgeway, the Ridgeway National Trail, the Icknield Way Path, the Peddars Way, and a small part of the Norfolk Coast Path to form a path that he calls the Greater Ridgeway, with a length of approximately 365 miles from Lyme Regis to Hunstanton.
Because parts of the Ridgeway National Trail and the Icknield Way Path are only usable as a footpath, an Icknield Way Path Riders Route or Icknield Way Trail has been created for horseriders and cyclists. The route runs from Bledlow to Roudham Heath, where it joins the Peddars Way Horseriders Route. 
- Article about Anglo-Saxon Wantage with maps indicating street layout with the Icknield Way and a street with the name (Ickleton) clearly derived from it.
- S. Harrison, "The Icknield Way: some queries", The Archaeological Journal, 160, 1-22, 2003.
- K. Matthews, Circular Walk (Wilbury Hill, Ickleford, Cadwell, Wilbury Hill).
- R. Bradley, Solent Thames Research Assessment - the Neolithic and Early Bronze Age, 2008.
- Rhiannon, The Icknield Way: Miscellaneous, 2008.
- A. Mawer and F. M. Stenton, The Place-names of Bedfordshire and Huntingdonshire, English Place-name Society 3, 1926, ISBN 0-904889-47-5, pp. 4-5.
- Cotton Nero D.i, f186v. The map is discussed on pages 62-63 of O. Roucoux, The Roman Watling Street: from London to High Cross, Dunstable Museum Trust, 1984, ISBN 0-9508406-2-9.
- Icknield Way Morris Men, Prehistory - Ancient Paths.
- Icknield Way Path (a series of three leaflets for riders), Countryside Commission, 1992.
- E. Thomas, The Icknield Way, Constable, 1916.
- R. Quinlan, The Greater Ridgeway: A Walk along the Ancient Route from Lyme Regis to Hunstanton, Cicerone, 2003, ISBN 1-85284-346-2.
- S. Jennett, The Ridgeway Path, HMSO for Countryside Commission (Long-Distance Footpath Guide 6), 1976, ISBN 0-11-700743-9.
- North Chilterns Trust, The Icknield Way Trail: Bedfordshire and West Hertfordshire, c. 2007.
- Long Distance Walkers Association, Icknield Way Trail.
- British Horse Society, Icknield Way Riders' Way and Peddars Way (National Trail).
- Buckinghamshire County Council, The Icknield Way.
- Clarke WG: In Breckland Wilds, Heffer, Cambridge; 2nd edition, 1937; p.67.