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Maintaining Na+/K+ homeostasis is a critical feature for plant survival under salt stress, which depends on the operation of Na+ and K+ transporters. Although some K+ transporters mediating root K+ uptake have been reported to be essential to the maintenance of Na+/K+ homeostasis, the effect of K+ long‐distance translocation via phloem on plant salt tolerance remains unclear. Here, we provide physiological and genetic evidence of the involvement of phloem‐localized OsAKT2 in rice salt tolerance. OsAKT2 is a K+ channel permeable to K+ but not to Na+. Under salt stress, a T‐DNA knock‐out mutant, osakt2 and two CRISPR lines showed a more sensitive phenotype and higher Na+ accumulation than wild type. They also contained more K+ in shoots but less K+ in roots, showing higher Na+/K+ ratios. Disruption of OsAKT2 decreases K+ concentration in phloem sap and inhibits shoot‐to‐root redistribution of K+. In addition, OsAKT2 also regulates the translocation of K+ and sucrose from old leaves to young leaves, and affects grain shape and yield. These results indicate that OsAKT2‐mediated K+ redistribution from shoots to roots contributes to maintenance of Na+/K+ homeostasis and inhibition of root Na+ uptake, providing novel insights into the roles of K+ transporters in plant salt tolerance. In Oryza sativa, a Shaker K+ channel, OsAKT2 mediates K+ redistribution from shoots to roots, contributing to maintenance of Na+/K+ homeostasis and inhibition of root Na+ uptake under salt stress. [ABSTRACT FROM AUTHOR]