John Blackwall (20 January 1790 – 11 May 1881) was an English naturalist with a particular interest in spiders.

He was interested in nature from an early age, first in birds and then spiders, on which he published his first article in 1827.

Ten of the plates included were by Octavius Pickard-Cambridge and twelve were by the Irish naturalist Robert Templeton.

Adult spiders of the same species differ so remarkably in size and colour, and that independently to all appearance of the situations in which they are found, that I am unable to assign an adequate cause for this extraordinary fact...Blackwall's work constituted a significant stage in the emergence of arachnology.

He was one of the first to be interested in spiders of very small sizes, in particular those belonging to the genera Neriene and Walckenaeria.