The Someș or Szamos is a left tributary of the Tisza in Hungary and Romania. It has a length of 415 km (258 mi), of which 50 km are in Hungary. The Someș is the fifth largest river by length and volume in Romania. The hydrographic basin forms by the confluence at Mica, a commune about 4 km upstream of Dej, of Someșul Mare and Someșul Mic rivers. Someșul Mic originates in the Apuseni Mountains, and Someșul Mare springs from the Rodna Mountains.

The Tisza, Tysa or Tisa, is one of the major rivers of Central and Eastern Europe. It was once called "the most Hungarian river" because it used to flow entirely within the Kingdom of Hungary. Today, it crosses several national borders.