Theodor Ilgen (29 October 1854, in
Brotterode – 19 September 1924, in
Miltenberg) was a German
archivist and historian.
He studied history at the
University of Marburg as a pupil of
Conrad Varrentrapp. In 1879 he received his doctorate, and afterwards worked as an archivist at the state archives in
Marburg (from 1880),
Düsseldorf (from 1882) and
Münster (from 1885). From 1900 to 1921 he was director of the archives at Düsseldorf.[1][2]
Die neuen Dienstgebäude der Staatsarchive zu Coblenz und Düsseldorf (with Richard Knipping, 1907) – The new offices of the State Archives at
Coblenz and Düsseldorf.
Die wiederaufgefundenen Registerbücher der Grafen und Herzöge von Cleve-Mark (1909) – The rediscovered registration books of the counts and dukes of the
Duchy of Cleves.
Quellen zur inneren Geschichte der Rheinischen Territorien: Herzogtum Kleve (2 parts, 1921–25) – Sources for the internal history of the Rhenish territories: Duchy of Cleves.[1][4]