Monomorphic or Monomorphism may refer to:
- Monomorphism, an injective homomorphism in mathematics
- Monomorphic QRS complex, a wave pattern seen on an electrocardiogram
- Monomorphic, a linguistic term meaning "consisting of only one morpheme"
- Monomorphic phenotype, when only one phenotype exists in a population of a species
- Sexual monomorphism, when both biological sexes are phenotypically indistinguishable from each other.