Friedrich Christian Diez (Giessen 1794 – Bonn 1876) was born into a family of theologians, judges, and government officials. He was trained in classical philology between 1811 and 1816 at the university of his native town. As a student he voluntarily took up arms against Napoleon (1814) and joined the Schwarzen of the Teutschen Lesegesellschaft. He redirected his studies towards modern languages at the University in Göttingen (1816-18) and translated Byron’s The corsair and Lara. After having been a private tutor in Utrecht and a Privatdozent back in Giessen, he obtained a doctoral degree in 1821 for his translation of Altspanische Romanzen. From 1825 on he was professor in Italian, Spanish and Portuguese at the university in Bonn; in 1830 he was appointed to the newly established chair in Romance philology at the same university.

Diez’s interest in medieval Romance literature was aroused by Jacob Grimm, with whom he entered into correspondence in 1817, by a meeting with Goethe in Thüringen (1818), who directed his attention towards Provençal, by A.W. Schlegel’s linguistic study of Occitan, and by Raynouard’s 1820 edition of troubadour poetry. He saw some such poems for himself in manuscript during a visit to Paris (1824) and printed them as Die Poesie der Troubadours (1826). This edition was followed by historical-genetical studies: Die Poesie der Troubadours (Zwickau 1826; 2nd ed. Leipzig 1883; translated by Roisin into French, 1845) and Leben und Werke der Troubadours (Leipzig 1829, 2nd ed. 1882).

These studies marked a shift in his interests from aesthetic appreciation to philological analysis, and led him to dedicate his life to Romance philology. Most important were his seminal Grammatik der romanischen Sprachen (3 vols, Bonn 1836-44, with later re-editions; English tr. 1862; French tr. 1872-76) and Etymologisches Wörterbuch der romanischen Sprachen (2 vols, Bonn 1853; 3rd ed. 1869-70). In both, Diez followed the historical-comparative method introduced by Grimm, enabling him to emphasize palaeo-Germanic elements in Romance languages. While allowing for exceptions to the linguistic laws (often attributed by him to euphony or Zweckmäßigkeit), his classification of the Romance languages into Italian, Spanish-Portuguese, and French-Provençal tended to compartmentalize fluid dialect variants into fixed categories. Next to these linguistic milestones, Diez continued his work as a textual critic, publishing a text corpus with glossaries of old Romance (1846, 1852, 1865) and a Portuguese literary history (Über die erste portugiesische Kunst- und Hofpoesie, 1863).

Diez’s contribution to Romance philology is often called epochemachend, though his influence only started belatedly after 1865, in part through his students, who helped to break the dominance of classical languages in France. Among these were Hugo Schuchardt and Gaston Paris, who co-founded the scientific journal Romania (1872). An international Diez-Stiftung was founded in Berlin in 1880.