John Sydenham (25 September 1807– 1 December 1846)[1] was an English antiquary.
In 1840 Sydenham left the Dorset Chronicle and became editor of The West Kent Guardian, a Greenwich paper.
He was one of the early members of the British Archæological Association.
In 1841 he wrote Baal Durotrigensis (London), a dissertation on the Cerne Abbas Giant, in which he endeavoured to discriminate between the primal Celtæ and the later Celto-Belgæ, who emigrated from Gaul.
Sydenham was the eldest son of John Sydenham, a bookseller of Poole, Dorset, born on 25 September 1807.