In this study, borate was found to selectively increase the stability of ribose over other aldopentoses. Ribose is the only sugar present in both early RNA-based biochemistry and contemporary DNA-based life, and the stability of ribose is of fundamental concern for determining the origin of early RNA-based biochemistry. The formose reaction is a potential process in the prebiotic synthesis of ribose and its stereoisomers arabinose, xylose, and lyxose. Ribose is the least stable of these aldopentoses, raising the fundamental question of whether it was originally a component of primitive RNA or was selected through biotic processes. Borate is known to increase the stability of aldopentoses, but the specific differences in the stabilization achieved among different stereoisomers remain unclear. In this study, it was found that the stabilities of all of the tested pentoses increased with the concentration of added borate, but notably, the stability of ribose increased the most. The predominant formation of complexes between borate and ribose was verified, in agreement with previous studies. This borate complex formation might have sequestered ribose from the isomerization and decomposition reactions, resulting in its selective stabilization. These findings indicate that ribose could have accumulated in borate-rich environments on the early Earth and suggest that ribose-based nucleotides combined with phosphate and nucleobases formed abiotically.