Moin is a Low Saxon greeting from East Frisia, the eastern Netherlands, North Frisia and Flensburg, meaning hello. Its use spread during the first half of the 20th century over the whole of northern Schleswig-Holstein; it is also used in the Danish dialect, Southern Jutish . Due to the German comic character Werner (who always greets with moin), since the 1980s it is used more and more in central Europe as well.

The word derives from the East Frisian Low Saxon word mooi, meaning beautiful. The original forms mooien Dag, mooien Abend, mooien Mor(g)en had been shortened to Moin. Therefore, Moin can be used 24 hours a day. The duplication Moin Moin is used as emphasis and for a more polite form as well. In Southern Jutish, Moin is used for hello and good bye, but Moin Moin is solely used for good bye.

People in more southern parts of Germany often mistakenly assume that Moin is a short from of Morgen (meaning "morning") and should be used like "good morning".

MoinMoin is a wiki engine. The name was chosen because of its "WikiWikiNess".

Moin is also the name of a serpent in Norse mythology, see Nidhogg.