Lewisham is one of the largest of the inner London boroughs, with an area of 13.7 square miles. It lies south-east of the City, between Southwark to the west, Greenwich to the east, and Bromley to the south. There is a short frontage to the Thames in the north. The 2001 census estimated the population at just under 250,000, of whom nearly a quarter described themselves as black or black British.

It is a young population, with an average age of 35, against a national 39. More than half the households are flats.

The borough comprises three old administrative parishes, St Mary Lewisham, St Margaret Lee, and St Paul Deptford. Lewisham and Lee had similar histories as farming villages turning gradually into fairly affluent suburbs, though Lewisham also had some industry in the eighteenth century, based upon the water power of the Ravensbourne. Lewisham and Lee were combined in 1900 to form the Metropolitan Borough of Lewisham. By that time the status of the area was changing under the pressure of improved transport services, of which trams were the most significant. The merchants and bankers who had been the typical nineteenth century residents were moving further out, and commercial clerks now formed the largest group.

Deptford was already a large industrial town while Lewisham and Lee were quiet villages. The huge growth of the population in the seventeenth and eighteenth centuries, based economically on the expansion of the Royal Dockyard, the Victualling Yard, which provisioned the Navy, and the various private dockyards, led to the building of the new church of St Paul, one of the Queen Anne churches. In 1730 this was separated from the ancient riverside parish of St Nicholas. The division was made by splitting in half the rateable value of the area. This meant that St Nicholas retained most of the closely built streets beside the Thames, with almost no scope for further growth, while St Paul received all the farmland in the south and west of Deptford. The result was that St Paul quickly became immensely more populous and wealthy than its mother parish.

In 1900 the parish of St Paul became the Metropolitan Borough of Deptford. This would have been a good moment to reunite the two Deptford parishes, but because the population of Greenwich was below the average it was decided to add St Nicholas to Greenwich to bring the borough totals closer to equality. As a result the 1730 division of Deptford still remains in force, although there have been boundary adjustments in recent years, one of which has transferred the old Royal Dockyard site from Greenwich to Lewisham.

The present London Borough of Lewisham was created in 1965, by the amalgamation of the Metropolitan Boroughs of Lewisham and Deptford. This was not so painless as the junction between Lewisham and Lee in 1900. There were objections on both sides, because of the very different social and political situations of the two districts, and because historic Deptford objected to having its identity submerged in Lewisham, but forty years have done much to smooth the differences.