Iso suomen kielioppi

Iso suomen kielioppi (lit. "the large grammar of Finnish") is a reference book of Finnish grammar. It was published in 2004 by the Finnish Literature Society and to this date is the most extensive of its kind. It is a collaboration written by noted Finnish language scholars Auli Hakulinen, Maria Vilkuna, Riitta Korhonen, Vesa Koivisto, Tarja-Riitta Heinonen and Irja Alho.

The 1,698 page book differs from earlier grammars by taking a descriptive approach and describing colloquial Finnish in addition to standard literary Finnish.

The entire work is also freely available online.