Co-dominance and the closely related incomplete dominance are terms in genetics that refer to the situation where an organism inherits a combined or blended phenotype instead of just the dominant trait, when two different alleles are present in the genotype. In the case of co-dominance, the characteristics defined by the alleles are both individually expressed though in different locations on the offspring organism. For example, the offspring of a cow with black fur and another with white fur may generate an offspring with a spotted pattern of black and white. Both of the alleles are fully expressed in the phenotype in this case, with one allele dominating the other in some instances, and the other allele dominating in others.

For a more detailed treatment, see Dominance relationship.