Sir Frederick John Owen Evans KCB FRS FRAS FRGS RN (9 March 1815 – 20 December 1885), was an officer of the Royal Navy.

In 1841 Evans was appointed master of HMS Fly, and for the next five years he was employed in surveying the Coral Sea, the Great Barrier Reef of Australia, and Torres Straits.

[3] After a short spell of duty in the Isle of Man, Evans returned, in 1847, in HMS Acheron, under Admiral Stokes, to New Zealand, where he was engaged for four years in surveying the Middle and South Islands.

During the Crimean War he served in the Baltic Sea, receiving the special thanks of Sir Charles Napier for his share in piloting the fleet through Åland.

He understood the need for studies of the effects of magnetic materials on ships' compasses at a period when the Navy was being revolutionised by the shift from wooden to iron construction.

He contributed five papers, all dealing with the magnetism of ships, to the Philosophical Transactions of the Royal Society, of which he was elected a fellow in 1862.

In 1865 he was appointed Chief Assistant to the Hydrographer to the Admiralty, Captain George Henry Richards, while continuing to the head of the magnetic department.

This treated of the magnetic character of the various iron ships in the navy, and also of the SS Great Eastern, and was his first work to be published in the Philosophical Transactions of the Royal Society.

He compiled the magnetical instructions for the observers on board HMS Challenger in 1872,[2] and delivered a lecture on the 'Magnetism of the Earth' to the Royal Geographical Society in 1878.