Admiral of the Fleet Sir Henry Bradwardine Jackson, GCB, KCVO, FRS (21 January 1855 – 14 December 1929) was a British Royal Navy officer.

He was advisor on overseas expeditions planning attacks on Germany's colonial possessions at the start of the First World War and was selected as the surprise successor to Admiral Lord Fisher upon the latter's spectacular resignation in May 1915 following the failure of the Gallipoli Campaign.

He had a cordial working relationship with First Lord of the Admiralty (and former Prime Minister) Arthur Balfour, but largely concerned himself with administrative matters and his prestige suffered when German destroyers appeared in the Channel, as a result of which he was replaced in December 1916.

[2] Promoted to sub-lieutenant on 18 October 1874, he was posted to the corvette HMS Rover on the North America and West Indies Station in August 1876.

[2] Promoted to again to lieutenant on 27 October 1877,[3] he joined the corvette HMS Active on the Cape of Good Hope Station in March 1878 and saw action ashore during the Anglo-Zulu War in 1879.

[13] He had a cordial working relationship with First Lord of the Admiralty (and former Prime Minister) Arthur Balfour but largely concerned himself with administrative matters and his prestige suffered when German destroyers appeared in the Channel.