Understanding and properly modeling excited-state dynamics is important for many photoinduced processes in chemistry and biochemistry including photochemistry, 1,2 light-harvesting, photocatalysis, photosensing, 9 vision, DNA photostability, and nonadiabatic electron transfer. Multiconfiguration pair-density functional theory (MC-PDFT) is a post-SCF method that that has been shown to be a computationally efficient method for computing potential energy surfaces (PESs) of excited states. Starting from a multiconfigurational wave function, such as that provided by the complete active space SCF (CASSCF) method, MC-PDFT computes a corrected energy through a nonvariational energy expression which is a functional of the electron density (ρ) and on-top pair density (Π). Consequently, the MC-PDFT energies are not eigenvalues of any particular Hamiltonian or quantum operator, and the energy of each state is computed independently of the other states involved in the calculation. MC-PDFT and its hybrid counterpart (HMC-PDFT) have been shown to perform similarly to the much more expensive n-electron valence perturbation theory (NEVPT2) for over 300 vertical excitations in the QUESTDB database. When modeling photochemistry and photodynamics, one frequently encounters locally avoided crossings and conical intersections: regions in which states of the same spin symmetry interact strongly with each other. This necessitates the use of an electronic structure method that includes state interaction to prevent unphysical PES crossings near these strong coupling geometries. Such methods are called multi-state methods, and they include multistate and quasi-degenerate perturbation theory as well as multireference configuration interaction. They are necessary for a proper treatment of nonadiabatic dynamics or The original MC-PDFT method is a single-state method, but recent research has provided multi-state extensions. State-interaction PDFT was the first such extension, and involved two sets of orbitals for the ground and excited states. Later, methods involving only a single set of state-averaged CASSCF (SA-CASSCF) orbitals were constructed and these are called multi-state PDFT (MS-PDFT). The MS-PDFT methods diagonalize an effective model space Hamiltonian matrix in an intermediate basis where the off-diagonal elements come from the underlying wave function theory, and the diagonal elements are replaced with the MC-PDFT energies of the intermediate states. The various MS-PDFT methods differ only in the choice of intermediate states, and the results are sometimes sensitive to this choice.