The title of Earl of Dartmouth was created in the Peerage of Great Britain in 1711 for William Legge, 2nd Baron Dartmouth, who was then Secretary of State for the Southern Department.

The Earl holds the subsidiary titles of Viscount Lewisham (1711) and Baron Dartmouth (1682), the latter in the Peerage of England.

The family seat is Woodsome Hall in Yorkshire.

Barons Dartmouth (1682)

• George Legge, 1st Baron Dartmouth (1647-1691)
• William Legge, 2nd Baron Dartmouth (1672-1750) (became Earl of Dartmouth in 1711)

Earls of Dartmouth (1711)

• William Legge, 1st Earl of Dartmouth (1672-1750)
• William Legge, 2nd Earl of Dartmouth (1731-1801)
• George Legge, 3rd Earl of Dartmouth (1755-1810)
• William Legge, 4th Earl of Dartmouth (1784-1853)
• William Walter Legge, 5th Earl of Dartmouth (1823-1891)
• William Heneage Legge, 6th Earl of Dartmouth (1851-1936)
• William Legge, 7th Earl of Dartmouth (1881-1958)
• Humphrey Legge, 8th Earl of Dartmouth (1888-1962)
• Gerald Humphrey Legge, 9th Earl of Dartmouth (1924-1997)
• William Legge, 10th Earl of Dartmouth (b.1949)