ENNEN, LEONHARD. - Priest and historian, b. at Schleiden on 5 March 1820, d. at Cologne on 14 June 1880. He was one of the founders of the *Historienses Vereni* of the Lower Rhine. He took a special interest in the history of the city and diocese of Cologne.
He wrote a history of the Reformation within the diocese (*Geschichte der Reformation im Bereiche der alten Erzbischöfe Köln*, Cologne 1849), a history of Cologne in five volumes (*Geschichte der Stadt Köln*, 1875–1886), and collected documents on the city’s history, a collection that in six volumes extends to 1897 (*Quellen zur Geschichte der Stadt Köln*, 1870–1907).
Bibl.: H. Kucsson, s. V. in *Allgemeine Deutsche Biographie*, XLVIII, pp. 380–382.