Solitary bees count for about 85% of all bee species, and as the most important pollinators of entomophilous plants, they play an irreplaceable role in maintaining the ecosystem. Although they are numerous pollinators of exceptional quality, only a small number of species are used for commercial purposes of pollinating plantations. Solitary bees are distributed all over the world and, unlike honey bees, they do not live in colonies, but each individual solitary bee builds a separate nest. Genera and species differ from each other in size, appearance, pollen preferences and life cycle. The aim of this study was to provide an overview on the most important species of solitary bees, their importance for the ecosystem and agriculture, as well as the impact of environmental factors on their life. Recently, the number of solitary bees is decreasing as a result of their natural habitats being destroyed by anthropogenic influences, the discrepancy between the flowering period and the emergence of bees caused by climate change, and the increasing mortality of individuals due to frequent use of broad-spectrum pesticides. Diseases and pests also pose a potential threat for solitary bees.