Constraint may refer to:

• Constraint (computer-aided design), a demarcation of geometrical characteristics between two or more entities or solid modeling bodies
• Constraint (mathematics), a condition of an optimization problem that the solution must satisfy
• Constraint (mechanics), a relation between coordinates and momenta
• Constraint (computational chemistry)
• Constraint (information theory), the degree of statistical dependence between or among variables
• Constraints (journal), a scientific journal
• Constraint (database), a concept in relational database

• Biological constraints, factors which make populations resistant to evolutionary change
• Carrier's constraint on lung function in long thin animals
• Finite domain constraint, in mathematical solution-finding
• Integrity constraints in databases
  • Check constraint
  • Foreign key constraint
• Observational constraint in science, a constraint on a solution implied by previous observations
• Specific types of mechanical constraints:
  • First-class constraint and second-class constraint in Hamiltonian mechanics
  • Primary constraint, secondary constraint, etc. in Hamiltonian mechanics
  • Holonomic constraints, also called integrable constraints, (depending on time and the coordinates but not on the momenta)
  • Nonholonomic constraints
  • Pfaffian constraint
  • Scleronomic constraint (not depending on time)
  • Rheonomic constraint (depending on time)

• Constrained optimization, in finance, linear programming, economics and cost modeling
• Constrained writing, in literature
• Constraint algorithm, such as SHAKE, or LINCS
• Constraint programming
• Constraint logic programming
• Constraint satisfaction, in computer science
• Constraint satisfaction problem
• Loading gauge, a constraint in engineering
• Optimality theory, in linguistics, a constraint-based theory which is primarily influential in phonology
• Restraint (disambiguation)
• Structure gauge, a constraint in engineering
• Theory of constraints, in business management