A relaxation technique is a method in mathematical optimization for relaxing a strict requirement, by either substituting for it another more easily handled requirement or else dropping it completely. Relaxation techniques are commonly used in place of branch and bound algorithms, or to obtain bounds in those algorithms.

Such relaxation techniques should not be confused with the unrelated relaxation methods used in solving elliptic partial differential equations.

Some relaxation techniques

• Linear programming relaxation
• Lagrangian relaxation
• Semidefinite relaxation