Thegan dari Trier (atau Degan dari Trèves) (sbl. 800^[1] – skt. 850) merupakan seorang rohaniwan Katolik Roma dari Franka dan penulis Gesta Hludowici imperatoris yang merupakan sumber utama kehidupan Ludwig yang Saleh, Kaisar Romawi Suci, putra dan penerus Charlemagne.

• Dutton, P. (2004). Carolingian civilization : a reader. Ontario: Broadview Press. ISBN 1-55111-492-5.
• Innes, M. (2002). ""He never even allowed his white teeth to be bared in laughter" : the politics of humour in the Carolingian Renaissance". Dalam G.Halsall (ed.). Humour, history and politics in late antiquity and the early Middle Ages. Cambridge: Cambridge University Press. ISBN 0-521-81116-3.
• McKitterick, R. (1994). Carolingian Culture. Cambridge: Cambridge University Press. hlm. 209–211. ISBN 978-0-521-40586-7.
• Mitchell, K.; Tremp, Ernst (1990). "Review of Studien zu den Gesta Hludowici Imperatoris des Trierer Chorbischofs Thegan by Ernst Tremp". Speculum. 65 (4). Medieval Academy of America: 1065–1066. doi:10.2307/2863638. JSTOR 2863638.
• Tremp, E. (1988). Studien zu den Gesta Hludowici imperatoris des Trierer Chorbischofs Thegan (dalam bahasa Jerman). Hannover: Hahn. ISBN 3-7752-5154-5.
• Tremp, E. (1990). "Thegan und Astronomus, die beiden Geschichtsschreiber Ludwigs des Frommen". Dalam R. Collins (ed.). Charlemagne's Heir. Oxford: Clarendon Press. ISBN 0-19-821994-6.
• Tremp, E. (1995). Thegan. Das Leben Kaiser Ludwigs ; Astronomus ; herausgegeben und übersetzt (dalam bahasa Jerman). Hannover: Hahnsche Buchhandlung. ISBN 3-7752-5352-1.

• "Vita Ludovici imperatoris" in MGH^{[pranala nonaktif permanen]} Latin with German translation
•  Herbermann, Charles, ed. (1913). "Thegan (Degan) of Treves". Catholic Encyclopedia. New York: Robert Appleton Company.
• Opera Omnia by Migne Patristica Latina with analytical indexes Latin text without Walafrid's prologue
• Vita Hludowici imperatoris Another Latin text without Walafrid's prologue