Giardia spp. (Giardia duodenalis, G. lamblia, G. intestinalis) is a parasitic intestinal protozoan that causes giardiasis (lambliiasis), a disease that can lead to serious gastrointestinal problems in humans and acute and chronic health consequences. This pathogen is often transmitted through contaminated water for human consumption, making its presence in water a serious public health problem. Giardia spp. can be found in various water sources, including surface water, wells, reservoirs and even in treated waters, if the treatment is not adequate. The most common symptoms of giardiasis are watery diarrhea, cramps, nausea, vomiting, elevated body temperature, weight loss and dehydration. The clinical picture can vary from the complete absence of symptoms to the appearance of more severe symptoms. Giardiasis can be especially dangerous for risk groups, such as children, the elderly and immunocompromised people. Therefore, monitoring and controlling the presence of Giardia spp. in water is of vital importance for the preservation of public health. Regular water analysis, improvement of the purification system, as well as public education on risks and preventive measures are recommended in order to reduce the occurrence of giardiasis.