Eric Reginald Lubbock, 4th Baron Avebury, was an English politician and human rights campaigner. He served as the Liberal Member of Parliament for Orpington from 1962 to 1970. He then served in the House of Lords, having inherited the title of Baron Avebury in 1971, until his death. In 1999, when most hereditary peers were removed from the House of Lords, he was elected by his fellow Liberal Democrats to remain. When he died, he was the longest serving Liberal Democrat peer.

Baron Avebury, of Avebury in the County of Wiltshire, is a title in the Peerage of the United Kingdom. It was created 22 January 1900 for the banker, politician and archaeologist Sir John Lubbock, 4th Baronet. He was succeeded by his eldest son, the second Baron. On his death the titles passed to his nephew, the third Baron. He was the son of Harold Fox Pitt Lubbock, fourth son of the first Baron, who died in 1971. The title then passed to the third Baron's first cousin, the fourth Baron, the son of Maurice Fox Pitt Lubbock, sixth son of the first Baron. The fourth baron was a Liberal Democrat politician and one of the ninety excepted hereditary peers who remained in the House of Lords after the passing of the House of Lords Act 1999. He was succeeded by his son, the fifth Baron, in 2016.