The Oituz River is a tributary of the Trotuş River in Romania.
Oituz (formerly Grozeşti; Hungarian: Gorzafalva or Ojtoz) is a commune in Bacău County, Romania. It is composed of six villages: Călcâi (Zöldlonka), Ferestrău-Oituz (Fűrészfalva), Hârja (Herzsa), Marginea, Oituz and Poiana Sărată (Sósmező).
Oituz was the site of two battles during the First World War: the First and Second Battle of Oituz.
According to Iorgu Iordan, the commune's name is of Turkic origin; otuz or oltuz means "thirty" in Turkish.
At the 2002 census, 99.8% of inhabitants were ethnic Romanians and 0.2% Hungarians. 49.2% were Romanian Orthodox, 48.9% Roman Catholic and 1.8% Seventh-day Adventist.
Coordinates: 46°12′N 26°37′E / 46.200°N 26.617°E / 46.200; 26.617