The borough included most of Holborn (the parts outside the City of London) as well as Bloomsbury and St Giles.

The borough was formed in 1900 from seven civil parishes and extra-parochial places; all but the first of these were historically part of Holborn: In 1930 these seven were combined into a single civil parish called Holborn, which was conterminous with the metropolitan borough.

[1] Previous to the borough's formation it had been administered by two separate local bodies: Holborn District Board of Works and St Giles District Board of Works.

[2] The entrance gate piers to the church of St Giles-in-the-Fields commemorate the Borough when it was amalgamated in 1965, and bear an inscription to this effect, although the arch that bore the borough's arms has since been removed.

[3] Holborn was the smallest of the twenty-eight metropolitan boroughs of the County of London, with an area of between 405 and 407 acres (1.6 km2).