Unitary theory may refer to:
Physics Unitarity (physics), a restriction on any theory in physics that all probabilities must sum to one Unitary gauge, a particular choice of a gauge fixing in a gauge theory with a spontaneous symmetry breaking
Other uses Unitary executive theory, the theory of US constitutional law holding that the President has the power to control the entire executive branch Unitary theories of memory, hypotheses regarding short-term and long-term memory