John Blackwall (January 20, 1790 - May, 1881) was a British naturalist.

Blackwall lived at Llanrwst in north Wales from 1833 until his death. He was interested in nature from an early age, first in birds and then spiders, on which he published his first article in 1827.

He published A History of the Spiders of Great Britain and Ireland (2 vols., 1861-1864), which included accounts of 304 species and gave the first adequate descriptions of British spiders. Ten of the plates included were by Octavius Pickard-Cambridge.

The work of Blackwall constituted a significant stage in the emergence of araneology . He was one of the first to be interested in the spiders of very small sizes, belonging in particular to the kinds Neriene and Walckenaera.