Reciprocity theorem may refer to:

• Quadratic reciprocity, a theorem about modular arithmetic
  • Cubic reciprocity
  • Quartic reciprocity
  • Artin reciprocity
  • Weil reciprocity for algebraic curves
• Frobenius reciprocity theorem for group representations
• Stanley's reciprocity theorem for generating functions
• Reciprocity (engineering), theorems relating signals and the resulting responses
  • including Reciprocity (electrical networks), a theorem relating voltages and currents in a network
• Reciprocity (electromagnetism), theorems relating sources and the resulting fields in classical electromagnetism
• Tellegen's theorem, a theorem about the transfer function of passive networks
• Reciprocity law for Dedekind sums
• Betti's theorem in linear elasticity