Lucas Barrett (14 November 1837 – 19 December 1862) was an English naturalist and geologist. Barrett was born in London and educated at University College School. He went to Ebersdorf, near Lobenstein, Vogtland, Germany in 1853, studying botany and chemistry for a year. In 1855, he accompanied Robert MacAndrew on a dredging excursion from the Shetland Islands to Norway and beyond the Arctic Circle; he subsequently made other cruises, to Greenland and to the coast of Spain. These expeditions laid the foundations of an extensive knowledge of the distribution of marine life.