Chemical-based fertilizers are widely used to achieve maximum productivity in conventional agricultural systems. The excessive and continuous utilization of chemical-based fertilizers resulted in environmental pollution, increased costs, and hazards for both farmers and consumers. For this reason, researchers are interested in developing methods that employ beneficial soil fungi in place of chemical-based fertilizers to support the sustainability of the agricultural industry and the environment. The present study was aimed to isolate the mineral solubilizing fungi from rhizosphere soil in some agricultural areas in northern Thailand. Three new species in the genus Aspergillus section Nigri, namely Aspergillus chiangmaiensis, Aspergillus pseudopiperis, and Aspergillus pseudotubingensis, were obtained and identified using a polyphasic taxonomic approach with multilocus phylogenetic and phenotypic analyses. All fungi were evaluated for their ability to promote plant growth. The result revealed that all fungi were able to solubilize the insoluble mineral forms of calcium, copper, cobalt, iron, manganese, magnesium, zinc, phosphorus, feldspar, and kaolin. Aspergillus pseudopiperis could produce indole-3-acetic acid. All fungi were positive in terms of siderophore, endogulcanase, pectinase, and xylanase productions. Moreover, all fungi could enhance the growth of Arabidopsis in the laboratory. In greenhouse experiment, all fungi significantly increased growth and crop yield of onion and green oak lettuce as well as root induction in sugarcane and cassava cutting stems. Therefore, these fungi demonstrate the potential of biostimulators that can be applied as biofertilizers in the future.