The quantum-dot cellular automata (QCA) technology is a promising alternative technology to CMOS technology to extend the exponential Moore's law progress of microelectronics at nanoscale level, which is expected to be beneficial for digital circuits. This paper presents and evaluates three multiplexer architectures: a new and efficient 2:1 multiplexer architecture, a 4:1 multiplexer architecture, and 8:1 multiplexer architecture in the QCA technology. The 4:1 and 8:1 QCA multiplexer architectures are proposed based on the 2:1 QCA multiplexer. The proposed architectures are implemented with the coplanar crossover approach. These architectures are simulated using the QCADesigner tool version 2.0.1. The 2:1, 4:1, and 8:1 QCA multiplexer architectures utilize 15, 107, and 293 cells, respectively. The simulation results demonstrate that the proposed QCA multiplexer architectures have the best performance in terms of clock delay, circuit complexity, and area in comparison with other QCA multiplexer architectures.