Etheridge was born at Ross-on-Wye, in Herefordshire, the son of Thomas Etheridge and his wife Hannah Pardoe. After an ordinary school education in his native town, he obtained employment in a business house in Bristol. There he devoted his spare time to natural history pursuits.
At the Bristol Philosophical Institution for lectures, he encountered William Sanders and Samuel Stutchbury, and in 1850 was appointed curator of its museum. He also became lecturer on botany in the Bristol medical school. In 1857, through the influence of Sir Roderick I. Murchison, he was appointed to a post in the Museum of Practical Geology in London, and eventually became palaeontologist to the Geological Survey.
In 1865 he assisted Prof. Huxley in the preparation of a Catalogue of Fossils in the Museum of Practical Geology. His chief work for many years was in naming the fossils collected during the progress of the Geological Survey, and in supplying the lists that were appended to numerous official memoirs. In this way he acquired an exceptional knowledge of British fossils, and he ultimately prepared an elaborate work entitled Fossils of the British Islands, Stratigraphically and Zoologically Arranged. Only the first volume dealing with the Palaeozoic species was published (1888). Etheridge also was author of several papers on the Rhaetic Beds, and of an important essay on the Physical Structure of North Devon, and on the Palaeontological Value of the Devonian Fossils (1867). He edited, and in the main rewrote, the second part of a new edition of John Phillips's Manual of Geology entitled Stratigraphical Geology and Palaeontology (1885). He was elected Fellow of the Royal Society in 1871, was awarded the Murchison Medal of the Geological Society of London in 1880 and was president of that Society in 1881-1882. In 1881 Etheridge was transferred from the Geological Survey to the geological department of the British Museum, where he served as assistant keeper until 1891. In 1896 he was the first recipient of the Bolitho Medal of the Royal Geological Society of Cornwall.
His son Robert Etheridge, Junior was also a palaeontologist.
- BIOGRAPHICAL INDEX OF FORMER FELLOWS OF THE ROYAL SOCIETY OF EDINBURGH 1783 – 2002 (PDF). The Royal Society of Edinburgh. July 2006. ISBN 0 902 198 84 X.
- Chisholm, Hugh, ed. (1911). "Etheridge, Robert". Encyclopædia Britannica. 9 (11th ed.). Cambridge University Press.
- Cleevely, R. J. "Etheridge, Robert (1819–1903)". Oxford Dictionary of National Biography (online ed.). Oxford University Press. doi:10.1093/ref:odnb/33028. (Subscription or UK public library membership required.)