Eliezer Cogan (1762–1855), was an English scholar and divine.
Cogan was born at Rothwell, Northamptonshire, the son of John Cogan, a surgeon, then 64 years old. The father, who survived until 1784, and was the author of An Essay on the Epistle to the Romans and of other anonymous pieces, married twice; by his first wife he had a son Thomas Cogan the physician, and by the second he was the father of Eliezer. The boy studied Latin grammar before he was six years old. For six months he was placed at Market Harborough in the school of Stephen Addington, but his early life was mainly passed under his father's roof, and he was self-taught in the rudiments of Greek.
To complete his education he was sent to Daventry Academy, where he was for six years, three as pupil and three as assistant tutor, under Thomas Belsham. At this time there were about 50 pupils, many known in later life as Unitarians. When John Kenrick moved from Daventry to Exeter in 1784, his place was taken by Cogan, who thus became Belsham's colleague. In the autumn of 1787 Cogan was elected as minister of Presbyterian congregation at Cirencester, and continued in that position until 1789. During this period of his life he printed for his friends, though he did not publish, a Fragment on Philosophical Necessity.
On 21 September 1790 he married Mary, the daughter of David Atchison of Weedon, and in the following July he settled for a short time at Ware in Hertfordshire, but after a few months he moved first to Enfield and then to Cheshunt. Cogan was elected minister of the chapel in Crossbrook Street, Cheshunt, in 1800, and in January of the following year he was also appointed by the dissenting congregation at Walthamstow. During that year he preached alternately there and at Cheshunt, but then he transferred his school from Cheshunt to Higham Hill, Walthamstow, and ministered only to the congregation there.