A novel readout architecture that uses multiple nondestructive floating-gate amplifiers (FGAs) to achieve subelectron readout noise in a thick, fully depleted silicon detector is presented. This multiple-amplifier sensing charge-coupled device (MAS-CCD) can perform multiple independent charge measurements with each amplifier; measurements with multiple amplifiers can then be combined to further reduce the readout noise. This allows getting subelectron noise operation in less time compared with single-nondestructive-amplifier CCDs. The performance of this detector is demonstrated, emphasizing the ability to resolve individual quanta and to combine measurements across amplifiers to reduce readout noise. These characteristics make it a candidate technology for astronomical observations, quantum imaging, and low-energy interacting particles.