《X--未知的元素》 是Leslie Norman,Joseph Losey导演的作品，发行于1956年（英国），由Dean Jagger,Edward Chapman,Leo McKern,Anthony Newley等主演的一部科幻片。
讲述了： 　　British Army radiation drills at a remote Scottish base attract a subterranean, radioactive entity of unknown nature that vanishes, leaving two severely radiation-burned soldiers... and a "bottomless" crack in the earth. Others who meet the thing in the night suffer likewise, and with increasing severity; it seems to be able to "absorb" radiation from any source, growing bigger and bigger. What is it?? How do you destroy a thing that "feeds" on energy?