Ruukki is a former municipality of Finland.
It is located in the province of Oulu and is part of the Northern Ostrobothnia region. The municipality had a population of 4,505 (31 December 2006) and covered an area of of which is water. The population density was .
The municipality was unilingually Finnish.
In 2007 municipality of Ruukki joined together with Siikajoki.