One-gene heterosis, also known as single-gene heterosis or allele-specific heterosis, is a phenomenon in genetics where a hybrid plant with two different alleles for a particular gene exhibits superior traits compared to its parents. Synonyms for one-gene heterosis include allele-specific hybrid vigor, genetic overdominance, hybrid vigour, and allelic heterosis. This occurs when a dominant allele expressed in the hybrid plant provides a beneficial effect that is absent in both the parental plants. One-gene heterosis has important applications in crop breeding, as it can enhance yield, disease resistance, and quality traits. Understanding and utilizing one-gene heterosis can therefore play a significant role in improving agricultural productivity and sustainability.