The nature reserve Velký a Malý Tisý (Big and Small Tisý) was established for the protection of a lot of rare species of birds with their natural habitats on the banks of Velký Tisý (Big Tisý) and Malý Tisý (Small Tisý) ponds. It comprises both these ponds and some smaller ponds in the surroundings.
The reserve lies about 6 km north of the town Třeboň (on the left side along the road to the small town Lomnice nad Lužnicí) and it is 706 ha large. It is a part of the Protected Landscape Area Třeboňsko and it is protected by UNESCO as well.
The reserve is not open to the public (for better protection and peace of birdlife).