Poplar South (strictly South Poplar, although this is an unusual form of official name for a borough constituency) was a parliamentary constituency centred on the Metropolitan Borough of Poplar of the County of London. It returned one Member of Parliament (MP) to the House of Commons of the Parliament of the United Kingdom.
The constituency was created for the 1918 general election, and abolished for the 1950 general election. It was then largely replaced by a new Poplar constituency.
The Borough of Poplar wards of Bromley Central, Bromley South East, Poplar Cubitt Town, Poplar East, Poplar Millwall, Poplar North West, and Poplar West.