The town was the site of a small Roman fort, Blestium, and became established after the Normans built Monmouth Castle c. 1067.

[2] Excavations undertaken by the Monmouth Archaeological Society on sites along Monnow Street have uncovered details of the early history of the town.

[3] Evidence of a Bronze Age boat building community, including three 100-foot-long (30-metre) channels adjoining the site of a now-vanished lake, was discovered in September 2013, during archaeological investigations by the Monmouth Archaeological Society of the Parc Glyndwr housing development site, immediately north-west of the town.

[5][6] Oak timbers had been "skillfully" cut with stone or flint axes to form stilts, of posts and poles, which "probably" rested on three parallel fully-grown tree 'sleeper beams', up to 3 feet 3 inches (1 m) wide, laid horizontally on the lakebed.

The only evidence of continuing settlement at Monmouth is a record of a 7th-century church, at an unknown location within the town, dedicated to the Welsh saint Cadoc.

A town grew up around it, and a Benedictine priory was established around 1075 by Withenoc, a Breton who became lord of Monmouth after Roger, the son of William fitzOsbern, was disgraced.

[8] The priory may have once been the residence of the monk Geoffrey of Monmouth, who was born around 1100 and is best known for writing the chronicle Historia Regum Britanniae ("History of the Kings of Britain").

[8] Charters from the period refer to the town's trade in iron, and to forges making use of local ore and charcoal.

The cinders produced by the forges formed heaps, and were used in building foundations; the name of Cinderhill Street in Overmonnow dates from this period.

[9][12] King Edward II was briefly imprisoned at Monmouth Castle in 1326 after being overthrown by his wife Isabella and her lover Roger Mortimer.

In 1387, John of Gaunt's grandson was born to Mary de Bohun, in the Queen's Chamber within the gatehouse of Monmouth Castle, while his father Henry Bolingbroke was hunting in the area.

The Shire Hall was built in 1724, and was used for the local Assizes, with the area beneath the building serving as the town market.

[12][16] The town was visited in 1802 by Admiral Horatio Nelson, who knew the importance of the area's woodland in providing timber for the British Navy and approved a Naval Temple built in his honour on the nearby Kymin Hill.

[10] Until the establishment of an official police force in 1857, Monmouth had a parish constable assisted by beadles to keep law and order.

The types of crime that Fuller and subsequent police officers had to deal with in and around Monmouth as the century progressed were recorded in detail in the local newspapers, the Merlin and the Monmouthshire Beacon.

These crimes included theft of livestock, clothing, food, valuables, fuel (wood and coal); assault; vandalism; highway robbery; fraud; passing counterfeit coin; prostitution, and indecent exposure, as well as the more serious crimes of concealing the death of an infant, carnal knowledge without consent, and murder.

[21] In the late 19th and early 20th centuries, Monmouth had close links with the Rolls family, who built a mansion at The Hendre just outside the town.

In 1904, Charles Rolls established a new car making business with Henry Royce, but in 1910 he was killed in an aeroplane crash at the age of 32; he is commemorated by a statue in Agincourt Square.

St Mary's Church contains a memorial to the men of who died in HMS Monmouth, which was sunk with all hands on 1 November 1914, by German cruisers SMS Scharnhorst and SMS Gneisenau off the Chilean Coast at the Battle of Coronel during the First World War; the church hosts an annual service in remembrance.

[28] The town centre itself is sited on a low-lying spur between the floodplains of the Wye and Monnow, and has frequently suffered from severe flooding.

[29] The water-meadows to the north and south of the town centre, known respectively as Vauxhall Fields and Chippenham Mead, have generally remained free of development.

[30] In climatic terms, the town is located between those areas around the Severn Estuary which show a maritime influence, and the cooler and drier conditions of the English Midlands further inland.

Regular but infrequent bus services run between the town and Hereford, Ross-on-Wye, Coleford, Chepstow, Newport and Abergavenny.

The wool industry was important in its early growth, and the town was a centre for the production of the very popular knitted and felted Monmouth caps, from the 15th century onwards.

[48] The Monmouth and District Chamber of Trade and Commerce represents businesses in the town and aims to support and encourage their development.

[61] The Bridges Community Centre in Drybridge House adjacent to the Health and Social Care Facility provides support services to disadvantaged and vulnerable people.

Both the Offa's Dyke Path, a long-distance footpath beginning in Chepstow and finishing in North Wales, and the Wye Valley Walk passing through the town.

[92] Gilbert de Clare, 6th Earl of Hertford and Guardian of England, died at the castle in 1295,[93] and King Edward II was briefly imprisoned there in 1326.

William Allen was awarded the Victoria Cross for his actions in the Battle of Rorke's Drift (1879), and is buried in Monmouth Cemetery.

[98] Other former or current residents of the area have included poet and singer-songwriter Jake Thackray, rugby international and commentator Eddie Butler, television presenter Kate Humble, historian and TV presenter Professor Saul David,[99] astrologer Russell Grant, historian Keith Kissack and comedian Miles Jupp.