German historian who was the founder of a renowned school of medievalists at the University of Göttingen. As the leading disciple of Leopold von Ranke's (Ranke, Leopold von) critical methods, he is regarded as the ablest of the German constitutional historians; many consider him to be superior to his teacher in exactness of scholarship.

Educated at the universities of Kiel and Berlin, Waitz was early influenced by Ranke. He began his researches in medieval German history while still a student, going to Hanover (1836) to assist in the work of publishing the Monumenta Germaniae Historica. Appointed to the chair of history at the University of Kiel in 1842, he became involved in politics; a fervent German nationalist, he sat in the provincial diet as a representative of his university (1846) and went to Berlin to represent the provisional government set up by the northern duchies of Schleswig in their revolt against the Danes. Elected by Kiel as a delegate to the national parliament at Frankfurt in 1848, he adhered to his party's policy for the unification of the German states under a German emperor, resigning only when the Prussian king refused the crown.

At Göttingen, where Waitz became a professor in 1849, his lectures and scholarship attracted many students and soon established the worldwide reputation of that university's historical school. His major work, Deutsche Verfassungsgeschichte, 8 vol. (1844–78; “German Constitutional History”), is an exhaustively annotated study of medieval German institutions from the earliest times to the middle of the 12th century, remarkable for its thoroughness. In 1875 he became editor of Monumenta Germaniae Historica. Other studies by Waitz include the important Schleswig-Holsteins Geschichte, 2 vol. (1851–54; “History of Schleswig-Holstein”), as well as numerous treatises on medieval German history.