The Duden ([ˈduːdən]) is a German dictionary, first published by Konrad Duden in 1880.
Currently the Duden is in its 24th edition and published in 12 volumes, each covering different aspects like loan words, etymology, pronunciation, synonyms, etc. The first of these volumes, the Die deutsche Rechtschreibung (Correct German Spelling) has long been the prescriptive source for the spelling of German.
The Duden is updated regularly, with new editions appearing every four or five years.
In 1902 the Bundesrat confirmed the Duden as the official standard for German spelling; Austria-Hungary and Switzerland soon followed suit.
In the ensuing decades, the Duden continued to be the de facto standard for German orthography. After World War II this tradition continued separately in East and West Germany in Leipzig and Mannheim.
In West Germany, some publishing houses began to attack the Duden "monopoly" in the 1950s, publishing dictionaries that contained alternative spellings. In reaction, in November 1955 the ministers of culture of the states of Germany confirmed that the spellings given by the Duden would continue to be the official standard.