Abstract <p>The article presents an analysis of different types of islands occurring in rivers with a branched channel or in meandering rivers, resulting in a classification of islands based on features of their formation, development, and dynamics, as well as characteristics of the river channel itself. Six main categories of islands are identified, defined by their properties and determined by their genesis, position in the channel, correspondence to a particular structural level of bifurcation, plan-form shape (hydraulic resistance exerted by the island on the flow), and age. In addition to the main factors, the classification of islands is also influenced by the characteristics of the river channel itself: its widening (the formation of an island in local channel widenings or as a result of bifurcation into two or more separate streams), stability, which determines the size and number of islands in each bifurcation node, which, in turn, is directly associated with the division of the flow between the distributaries. Separate categories are provided for the types of islands formed by sand or cobble-boulder deposits, which differ in the degree of resistance to fluvial action (intensity of erosion of the island head) and in the development of floodplain alluvium facies and floodplain soils, which determines the type and nature of vegetation on the island. The considered classification features represent the main function of the islands, i.e., flow bifurcation, and can be used in accounting of river water transportation.</p>