We developed an 8K 240-Hz full-resolution high-speed camera and slow-motion replay server system for the creation of sports content. The high-speed camera acquires 8K 240-Hz video through three 1.25-in 33-Mpixel 240-Hz CMOS image sensors. Signals are transmitted between a camera head and a camera control unit (CCU) through a four-core optical camera cable, and the CCU then processes the sensor signal and outputs an 8K 240-Hz RGB 4:4:4 video signal. The 8K 240-Hz slow-motion replay server system can record up to 240 min of 8K 240-Hz video while simultaneously playing back an 8K 60-Hz slow-motion video. The input 8K 240-Hz video is compressed by a factor of 12 and stored on solid-state drives. The replay server offers loop-recording, live-editing, and slow-motion replay functions with a dedicated remote controller. We evaluated the 8K slow-motion video by combining the camera and slow-motion replay server system.