Captain Henry Joseph Round (2 June 1881, Kingswinford, Staffordshire, England-17 August 1966, Bognor Regis) was one of the early pioneers of radio and received 117 patents. He was a personal assistant to Guglielmo Marconi.

Henry Joseph Round was the eldest child of Joseph and Gertrude Round and was born on 2 June 1881. He spent his early years in the small town of Kingswinford which is in Staffordshire, England. Henry Round undertook much of his early education at Cheltenham Grammar School. He later attended the Royal College of Science where he gained first class honors degree.

Round joined the Marconi Company in 1902 not long after Marconi had made his transatlantic wireless transmission. He was sent to the USA where experimented with a variety of different aspects of radio technology focusing on technologies such as dust cored tuning inductors. He also performed some experiments with transmission paths over land and sea at different times of the day and investigated direction finding for which he used a frame antenna. In some later experiments with cat's whisker detectors using a variety of substances, he passed current through them and noticed that some actually gave off light - the first time a light-emitting diode had been seen. Round reported this in the February 9, 1907 edition of Electrical World. This is the first known report of the effect of the light-emitting diode.

The First World War broke out in 1914 and Round was seconded to Military Intelligence with the rank of Captain. Using his experience in direction finding he set up a chain of direction finding stations along the Western Front. These stations proved so successful that another set was installed in England. Then in May 1916 they were monitoring transmissions from the German Navy at anchor at Wilhelmshaven. However on 30th May they reported a 1.5 degree change in the direction of the signals being perceived. When they heard of this the British Admiralty, the body controlling the Navy ordered the British fleet to set sail and engae them in Battle. The following day the Battle of Jutland was fought. It was the largest sea battle of all time.

For all his services during the war, Round was awarded the Military Cross. After the war Round returned to civilian life and became involved in radio transmitters and was heavily involved in the first broadcasts made in the United Kingdom.

For all his successes, Round was made Chief Engineer at Marconi in 1921, but some years later he decided to set up his own consultancy.

With war breaking out again in 1939, the British Government again called on his services. This time he was involved in ASDIC (Anti-Submarine Detection Investigation Committee) which is known today as Sonar.

Round died in August 1966 in a nursing home in Bognor Regis after a short illness.