1. Erasmus Ommanney was born in London in 1814, the seventh son in a family of eight sons and three daughters of Sir Francis Molyneux Ommanney, a naval agent and from 1818 to 1826 MP for Barnstaple, and his wife, Georgiana Frances, daughter of Joshua Hawkes.
Erasmus Ommanney was named after Admiral Sir Erasmus Gower who had mentored his uncle Admiral Sir John Acworth Ommanney.
Major General Edward Lacon Erasmus Ommanney Royal Engineers was his eldest brother and Prebendary George Druce Wynne Erasmus Ommanney was a younger brother.
Erasmus Ommanney entered the Royal Navy aged 12 in August 1826 under his uncle, Captain John Erasmus Ommanney, the captain of HMS Albion, which in December 1826 convoyed to Lisbon the troops sent to protect Portugal against the Spanish invasion.
The ship then went to the Mediterranean, and on 20 October 1827 Erasmus Ommanney took part in the Battle of Navarino aged just 13.
Erasmus Ommanney received the special commendation of the Admiralty for this dangerous service.
Erasmus Ommanney was promoted commander on 9 October 1840, and from August 1841 to the end of 1844 served on board the steam sloop HMS Vesuvius in the Mediterranean Sea.
Erasmus Ommanney was promoted captain on 9 November 1846, and from 1847 to 1848 was employed under the government commission during the Irish Famine, carrying into effect relief measures and the new poor law.
In 1845 Erasmus Ommanney was elected a Fellow of the Royal Geographical Society, and on 4 June 1848 he was elected a Fellow of the Royal Society.
On 25 August 1850 Erasmus Ommanney discovered the first traces of the fate of Sir John Franklin, which proved that his ships had wintered at Beechey Island when he discovered "fragments of stores and ragged clothing and the remains of an encampment".
In December 1851 Erasmus Ommanney was appointed Deputy Controller-General of HM Coastguard, holding this position until the Crimean War of 1854, when he commissioned HMS Eurydice as senior officer of a small squadron in the White Sea, where he blockaded Archangel, stopping the coasting trade, and destroyed Russian Government property.
On 14 January 1853 Erasmus Ommanney was elected a Fellow of the Royal Astronomical Society.
On 14 July 1871 Erasmus Ommanney was promoted to vice admiral, retiring on 1 January 1875.
Erasmus Ommanney was promoted to admiral on the retired list on 1 August 1877, in which year he was knighted for his scientific work in the Arctic.
Erasmus Ommanney had been elected FRS in 1868 for the same reason, and to the end of his life continued to take a great interest in geographical work and service subjects.
Erasmus Ommanney attended meetings of the Royal Geographical Society and the Royal United Service Institution, and for many years he was a councillor of both bodies, and of the British Association for the Advancement of Science.
Erasmus Ommanney died on 21 December 1904 at his son's home, St Michael's vicarage, St Michael's Road, Southsea, Hampshire, and was buried in Old Mortlake Burial Ground, which is in the London Borough of Richmond upon Thames.