English surgeon and naturalist, born in Greenwich, the second youngest of six sons of Samuel Collingwood, architect and contractor. He was educated at King's College School and later at Christ Church, Oxford (1845-1854), studying natural sciences and medicine. Collingwood continued his studies at Edinburgh University and Guy's Hospital before leaving the country to carry out research at medical schools in Paris and Vienna. He returned to England (1858) working briefly under Dr Thomas Addison at Guy's Hospital on what would become known as Addison's disease, then took a post as Lecturer in Botany (1859-1866) at the Royal Infirmary Medical School in Liverpool.

Collingwood volunteered as surgeon and naturalist for a scientific expedition (1866-1867) in HMS Serpent under Captain Charles Bullock, studying marine zoology and in particular nudibranch molluscs. After his return (1868) Collingwood tried to obtain a scientific position but was unsuccessful, so he returned to Liverpool and a post as senior physician at the Northern Hospital. He remained an active member of a number of learned societies and continued with his scientific publications and travels.

A religious man, Collingwood became a prominent Swedenborgian (New Churchman); from 1901 until shortly before his death he lived in Paris. Algal material was collected during the expedition on HMS Serpent and sent to J.D. Hooker, but these specimens were subsequently transferred to BM (c. 1961) under the terms of the Morton Agreement.