Klaus-Dieter Wirth (born October 28, 1940, Neuss, Germany) , philologist, linguist, and retired language teacher at the University of Düsseldorf. Writing haiku in German, English, French, Spanish, and Dutch since 1967. Member of seven national haiku societies and editor or contributor for fifteen European and North American journals. Has published some 400 poems, essays, and articles; currently has four quadrilingual haiku collections in print. His Der Ruf des Hototogisu: Grundbausteine des Haiku (2020) is a two-volume compendium of essays including more than 1,890 original and translated haiku. Resides in Viersen, Germany.