Earl Sondes, of Lees Court in the County of Kent, was a title in the Peerage of the United Kingdom. It was created in 1880 for the former Conservative Member of Parliament for East Kent, George Milles, 5th Baron Sondes. He was made Viscount Throwley, of the County of Kent, at the same time, which title was used as a courtesy title by the eldest son and heir apparent of the Earl. The titles became extinct on the death of his great-grandson, the fifth Earl, in 1996.

The title of Baron Sondes, of Lees Court in the County of Kent, was created in the Peerage of Great Britain in 1760 for Lewis Watson. Born the Hon. Lewis Monson, he was the second son of John Monson, 1st Baron Monson, and his wife Lady Margaret Watson, youngest daughter of Lewis Watson, 1st Earl of Rockingham (see these titles for earlier history of the families). In 1746 he assumed the surname of Watson on succeeding to the estates of his cousin, Thomas Watson, 3rd Earl of Rockingham (who was also Viscount Sondes). His son, the second Baron, represented Hedon in the House of Commons. His younger son, the fourth Baron, who succeeded his brother in 1836, assumed in 1820 by Royal licence the surname of Milles only. On his death the title passed to his son, the aforementioned fifth Baron, who was created Earl Sondes in 1880.

The sister of the 4th Earl Sondes, Lady Isobel Milles-Lade (d.1990), was married to the 18th Earl of Derby, of Knowsley Hall, Lancashire.

The family seat of the Earls Sondes was Lees Court, in the village of Sheldwich, three miles south of Faversham. The Lees Court Estate is today owned by the Countess Sondes, widow of the 5th and last Earl Sondes. Lees Court itself was entirely destroyed by fire in November 1910, but was carefully rebuilt and is now subdivided into private apartments. The Estate during the early 1900s was 85,000 acres. Today the Estate is 7,000 acres which includes the Swale Estuary and the Faversham and Oare Creeks.

• Lewis Watson, 1st Baron Sondes (1728–1795)
• Lewis Thomas Watson, 2nd Baron Sondes (1754–1806)
• Lewis Richard Watson, 3rd Baron Sondes (1792–1836)
• George John Milles, 4th Baron Sondes (1794–1874)
• George Watson Milles, 5th Baron Sondes (1824–1894) (created Earl Sondes in 1880)

• George Watson Milles, 1st Earl Sondes (1824–1894)
• George Edward Milles-Lade, 2nd Earl Sondes (1861–1907), died without male issue
• Lewis Arthur Milles, 3rd Earl Sondes (1866–1941), died without male issue
• George Henry Milles, 4th Earl Sondes (1914–1970)
• Henry George Herbert Milles-Lade, 5th Earl Sondes (1940–1996), died without issue, at which point all of his titles became extinct

• Baron Monson
• Viscount Monson
• Monson baronets
• Earl of Rockingham
• Earl of Feversham

• Kidd, Charles, Williamson, David (editors). Debrett's Peerage and Baronetage (1990 edition). New York: St Martin's Press, 1990.
• Leigh Rayment's Peerage Pages ^{[self-published source] [better source needed]}