James Eustace Bagnall ALS (7 November 1830 – 3 September 1918) was an English naturalist with a particular interest in botany, especially bryology.

A noted bryologist, he wrote the Handbook of Mosses in the Young Collector Series, various editions of which were published between 1886 and 1910.

He was the eldest son of James Bagnall (1804–1874) and his wife Jane Amelia (née Wall, 1806–1888).

"[4] He says of himself that "all my work, whether clerical or botanical, has been done in the scant leisure of a manufactory clerk" and that his "knowledge of botany has been self-acquired.

[6] Bagnall made important contributions to the Floras of the counties surrounding his home in Birmingham.

[5] Comprising 561 pages in three sections, this comprehensive work describes the topography, geology and meteorology of the county; divides it into districts based on drainage basins; lists the flora, including bryophytes, lichens and fungi, with most records broken down by district; and finishes with a detailed history of botanising in Warwickshire.

This 74 page work was intended to update Garner's Flora and contains a substantial number of new records, many by Bagnall himself.

[7] His most widely distributed work is his Handbook of Mosses, a contribution to The Young Collector Series published in London by Swan Sonnenschein, etc.