St Pancras South West was a constituency represented in the House of Commons of the Parliament of the United Kingdom.

It elected one Member of Parliament (MP) by the first past the post system of election.

The constituency comprised the south western part of the Metropolitan Borough of St Pancras.

In 1950 the constituency was split between Holborn and St Pancras South (wards Five and Seven) and St Pancras North (ward Four).

The political parties had been making preparations for an election to take place and by the Autumn of 1939, the following candidates had been selected;