This paper describes a solid-state image sensor for high-speed X-ray imaging. The sensor is made up of a light sensitive detector layer bump-bonded to a readout integrated circuit (ROIC). The detector layer is high resistivity n-type silicon and is fully depleted in operation. The p-implanted islands are used to define pixel regions with 100-μm × 100-μm area. The detector layer contains 852 × 209 pixels indium bump-bonded to four identical CMOS ROICs. Each ROIC contains 213 × 209 pixels and is fabricated using a 0.25-μm CMOS process. The ROIC utilizes a capacitive transimpedance amplifier-type front-end coupled to a switched capacitor analog memory. This architecture allows storage of eight frames for high-speed burst imaging of up to a million frames per second, followed by a slower multiplexed readout. Details of the sensor design and operation are presented together with characterization results. © 2014 IEEE.