Henry Alleyne Nicholson (September 11, 1844 - January 4, 1899) was a British palaeontologist and zoologist. The son of Dr. John Nicholson, a biblical scholar, was born at Penrith, Cumbria on September 11, 1844. He was educated at Appleby Grammar School and at the universities of Gottingen (Ph.D., 1866) and Edinburgh (D.Sc., 1867; M.D., 1869). Geology had early attracted his attention, and his first publication was a thesis for his D.Sc. degree titled On the Geology of Cumberland and Westmoreland (1868). In 1871 he was appointed professor of natural history in the University of Toronto; in 1874 professor of biology in the Durham College of Science and in 1875 professor of natural history in the University of St. Andrews. This last post he held until 1882, when he became Regius Professor of natural history in the University of Aberdeen. He was elected F.R.S. in 1897. His original work was mainly on fossil invertebrata (graptolites, stromatoporoids and corals); but he did much field work, especially in the Lake District, where he labored in company with Professor Robert Harkness and afterwards with Dr. John Edward Marr. He was awarded the Lyell Medal by the Geological Society in 1888. He died at Aberdeen on the fourth of January 1899. During his career he published 167 papers, usually as the sole author, and 12 textbooks. A revised version of Professor Nicholson's work The Ancient Life History of the Earth was re-published by eminent paleontologist Stephen Jay Gould in 1980. This article incorporates text from the Encyclopædia Britannica, Eleventh Edition, a publication now in the public domain.