The Lomnice river is the left tributary of the Otava river. It joins the Otava river ahead of the Zvíkov castle at the beginning of the Orlík Dam.
The Lomnice river springs on the slopes of Třemšín hill (827 m) in Central Bohemia, 733 m a.s.l. Then it flows to the south-east in the direction of the town Blatná and it feeds a lot of ponds in this region. Then it runs to the east through the hillycountry around the small town Mirotice and then it continues to the confluence with the Skalice river through the wooded valley. They join below the huge pine in the place called V Obouch. Then the Lomnice river flows into the Orlík Dam, which extends to the junction with the Otava river.
The Lomnice river is an important South Bohemian river. It is 60 km long and its drop is 387 m. It drains the river basin 831 square km large.
The part of the river from Blatná to the mouth to the Otava river is used for canoeing in summer. The blue marked trail leads along the river between the village Lučkovice (about 3 km north-west of Mirotice) and the confluence with the Skalice river in the protected area V Obouch.