A real-time hybrid optoelectronic analog-to-digital converter (HOE-ADC) based on optical sampling and electronic quantization is proposed and experimentally demonstrated. In the proposed HOE-ADC, a broadband semiconductor laser is intensity modulated by electronic pulses to generate an optical sampling pulse train. The optical sampling pulse is split into multiple channels with different optical fiber delay, and the analog signal is modulated on the multichannel optical sampling pulses using a Mach–Zehnder modulator array. By broadening the optical pulses, which can be done by employing optical-fiber chromatic dispersion, the bandwidth of the sampled pulse is reduced to match the sample rate of a low-speed electronic ADC, where the broadened optical sampling pulses are quantified. The nonlinearity of optical devices is calibrated through digital signal processing. A four-channel HOE-ADC is experimentally demonstrated. A sampling rate of 12  GS  /  s and a system bandwidth of 10 GHz are achieved. The effective number of bit (ENOB) for a 1.5-GHz target analog signal is measured to be 5.9 bit. Further, the primary influence factors, such as delay errors, for the performance of ENOB are also discussed.