German founder of modern textual criticism, or the methodology of determining the definitive text of a written work. His commentary (1850) on Lucretius' De rerum natura (“On the Nature of Things”) was perhaps his greatest achievement and has been regarded as a major accomplishment of Latin scholarship.

Professor at the Friedrich Wilhelm University, Berlin (1825–51), Lachmann devoted his life to the research of language—especially of Old and Middle High German—and literature. He laid down the rules of textual criticism and delineated the phonetic and metrical principles of Middle High German in early works of 1816–17. His clarification of his rigorous method in a number of works published between 1820 and 1836 led to the establishment of a school of textual criticism that gained many adherents.

In the area of classical studies he published editions of the poetry of Catullus and Tibullus (1829) and a number of other works. His views on Homer's Iliad, though no longer accepted, had considerable influence on Homeric criticism.