The title of Earl of Eltham has been created two times as a subsidiary title. The first creation was in the Peerage of Great Britain

Peerage of Great Britain

The Peerage of Great Britain comprises all extant peerages created in the Kingdom of Great Britain after the Act of Union 1707 but before the Act of Union 1800...

 in 1726 as a subsidiary title for the Duke of Edinburgh

Frederick, Prince of Wales

Frederick, Prince of Wales was a member of the House of Hanover and therefore of the Hanoverian and later British Royal Family, the eldest son of George II and father of George III, as well as the great-grandfather of Queen Victoria...

, eldest son of the Prince of Wales

George II of Great Britain

George II was King of Great Britain and Ireland, Duke of Brunswick-Lüneburg and Archtreasurer and Prince-elector of the Holy Roman Empire from 11 June 1727 until his death.George was the last British monarch born outside Great Britain. He was born and brought up in Northern Germany...

. This merged in the crown in 1760.

The second creation was in 1917 in the Peerage of the United Kingdom

Peerage of the United Kingdom

The Peerage of the United Kingdom comprises most peerages created in the United Kingdom of Great Britain and Ireland after the Act of Union in 1801, when it replaced the Peerage of Great Britain...

 for the Duke of Teck

Adolphus Cambridge, 1st Marquess of Cambridge

Adolphus Cambridge, 1st Marquess of Cambridge, GCB, GCVO, CMG , born Prince Adolphus of Teck and later The Duke of Teck , was a member of the British Royal Family and a younger brother of Queen Mary, the consort of King George V...

, brother of Queen Mary

Mary of Teck

Mary of Teck was the queen consort of the United Kingdom and the British Dominions, and Empress of India, as the wife of King-Emperor George V....

, who gave up his German titles for the British title of Marquess of Cambridge.

Earls of Eltham, First Creation (1726)

• Frederick, Prince of Wales
  Frederick, Prince of Wales
  Frederick, Prince of Wales was a member of the House of Hanover and therefore of the Hanoverian and later British Royal Family, the eldest son of George II and father of George III, as well as the great-grandfather of Queen Victoria...
  
   (1707-1751)
• George, Prince of Wales
  George III of the United Kingdom
  George III was King of Great Britain and King of Ireland from 25 October 1760 until the union of these two countries on 1 January 1801, after which he was King of the United Kingdom of Great Britain and Ireland until his death...
  
   (1738-1820), merged in crown 1760.

Earls of Eltham, Second Creation (1917)

• see Marquess of Cambridge