Lothar Johann Reinhard von Metternich (1551–1623) was the Archbishop-Elector of Trier from 1599 to 1623.
Lothar von Metternich was born in Schloss Vettelhoven in Grafschaft on 31 August 1551, the son of Johann von Metternich (1500-1562), Lord of Vettelhoven and bailiff of Saffenberg, and his fourth wife, Katharina von der Leyen zu Adendorf (1528-1567). He attended the University of Cologne from 1567 to 1577; the University of Perugia from 1577 to 1579; and the University of Padua from 1579 to 1581. In addition to his native German, he was fluent in Flemish, French, Italian, and Latin.
He became a Domizellar at the Cathedral of Trier in 1570; a canon of the cathedral in 1575; and Domscholaster in 1590. He was ordained as a priest on 13 June 1599.
Following the death of Archbishop of Trier Johann von Schönenberg, the cathedral chapter of the Cathedral of Trier elected Metternich as coadjutor archbishop on 7 August 1599. Pope Clement VIII confirmed his appointment on 11 October 1599. Bishop emeritus of Osor Coriolani Garzadori consecrated Metternich as a bishop on 30 July 1600 in the church dedicated to Florinus of Remüs in Koblenz.