Captain Z-Ro pronounced "Zero", is an American children's television show that ran locally onKRON in San Francisco beginning in November 1951, and was later nationally syndicated in the United States, ending its run of original episodes on June 10, 1956. It remained in syndication until 1960. Modeled on the science fiction space operas popular at the time (cf. Captain Video and Space Patrol), it featured sets and costumes emulating the futuristic designs of Buck Rogers and Flash Gordon.

Scientist Captain Z-Ro, working in his remote laboratory, safeguarded mankind and history from impending harm. He had a time machine, the ZX-99, both to view history and to send someone back in time. Each week, he and his teenage assistant Jet would view an episode in time and inevitably see that some event was unfolding contrary to history (e.g.,King John not signing the Magna Carta). Captain Z-Ro would then send Jet back in time to intervene and ensure that history played out as originally recorded. Over the years, plots involved Z-Ro and Jet rescuing a wide range of historical figures, including Genghis Khan, Marco Polo, Magellan, William the Conqueror, and Daniel Boone.

Like early episodes of Doctor Who, which premiered in the UK more than a decade later, most episodes were melodramatic history lessons for children. No serious effort was made to explain how the time machine worked, and time travel conundra (such as the grandfather paradox) were likewise glossed over. Each week after the last commercial, the announcer would intone: "Be sure to be standing by when we again transmit you to the remote location on planet Earth where Captain Z-Ro and his associates will conduct another experiment in time and space".