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Abstract. The classification of river basins considering their similar characteristics allows hypothesis tests on the similarity between hydrological systems, as well as better design of experimental and monitoring networks, and guides the selection of suitable models for certain hydrological systems. Thereby, the purpose of this study was to identify hydrologically homogeneous regions in the Solimões river basin, located in the Amazon region, using cluster analysis. Long-term mean flow (Qm) and flow with 90% of permanence(Q90) data of 30 gauge stations in the period from 1988 to 2007 were used to identify the homogeneous regions based on the Ward and K-means clustering methods on the Solimões river basin. In addition Qm and Q90 flows, the latitude and longitude values ​​of each station were also used as agglomerative characteristics, so that geographically distant stations could not form contiguous regions. The definition of the optimal number of clusters was done by plotting the value of the clustering criterion (MSE) in relation to the number of groups (g). For both analyzes, the optimum value of clusters found was of 6 clusters. The K-means and Ward methods returned identical results for the hydrologically homogeneous regions identified based on both the Qm and Q90 for the Solimões river basin. Three fluviometric stations located in the northern part of the basin were eliminated from the analysis because they were classified as a homogeneous region even though they were not contiguous areas. •  The Solimões river basin can be divided into five hydrologically homogeneous regions with respect to the mean and minimum flows.