This book proposes the reversible logic Multiplexer and also demarcates between reversible and irreversible logic Multiplexers. For power reduction in future computing technologies, reversible logic is a very productive approach of logic synthesis. The purpose of this book is to reduce power and area of 2:1 MUX, 4:1 MUX and reversible logic while maintaining the viable performance. The diverse configurations are designed using different topologies of 2:1 MUX and 4:1 MUX such as CMOS based MUX, transmission gate and pass transistor. The editors propose a new application of GDI (Gate-Diffusion Input) circuits to Reversible logic multiplexer with its Garbage input and output. The novel proposed design technique will consume less power than the other conventional gate. Reversible logic circuit has displayed less power dissipation in recent years. Additionally, this GDI cell technique decreases the power of the circuit, delay, Power-Delay Product (PDP) and it also compacts the frequency. The device scaling is partial as the power dissipations is more optimized in terms of delay, frequency jitter, bandwidth power supply, frequency and duty cycle of the signal and also establishes the noise of the circuit. In the reversible logic design, the GDI is efficient in lower delay, low power and low leakage current.