The London Borough of Islington was formed in 1965, when the former Metropolitan Boroughs of Islington and Finsbury were united as part of a London-wide reorganisation, but Islington's history is one of the oldest in London being mentioned in Domesday Book in the 11th century, and in an earlier Anglo-Saxon charter.

By the early Middle Ages substantial medieval houses had been built including Barnsbury manor house. After the dissolution of the monasteries, the surrounding lands were given to aristocratic families. By the sixteenth century it was a small village, known for harbouring recusants and fugitives. The local fields were used for illicit prayer meetings, training militia, fighting duels, archery and other sports . 

Its proximity to London and Westminster, gradually attracted rich and eminent residents. Thomas Cromwell lived at Canonbury in the 1530s, Henry Percy , 6th Earl of Northumberland (d. 1537), lived at Newington Green 1536-7. In the later 17th century Islington Spa (Clerkenwell), opposite Sadler's Wells , was developed as a resort. 

  In the eighteenth century it supplied London with butter, cream and milk. However, as London grew, brick terraces replaced the agricultural land and local farmers turned to manufacturing bricks and developing property. From the 1830s omnibuses were introduced for clerks and artisans to join merchants and professional men in living farther from their employment. 

The poor were also moving in, displaced by huge land clearances which established the great London railway stations. In the 1890s the northern part of the parish began to lose its middle-class residents to outer Middlesex, and large houses fell into multi-occupation. By 1903 Islington had the largest population of all the London boroughs, very little open space, and above average overcrowding. Few well-to-do people remained, except in Highbury and Canonbury,

Change was more rapid after the Second World War, when bombed sites could be used for new municipal housing. From the 1960s the southern part of Islington became popular with middle-class families. This ‘gentrification ’ was intensified by estate agents and speculators, and in Canonbury and Barnsbury working-class tenants were forced or encouraged to leave desirable terraces. Conservation areas were formed and traffic schemes put into operation, leading to the cosmopolitan and exciting Islington of today.