Langvatnet () is a lake that lies in Fauske Municipality in Nordland county, Norway. The lake lies about east of the town of Fauske. The village of Sulitjelma lies on the northeastern edge of the lake. Water from the lakes Kjelvatnet and LÃÂ¥mivatnet flow into the lake from the south and east. The water from Langvatnet flows out through the SjønstÃÂ¥ River to the west towards the lake ÃÂvrevatnet.