In an African desert millions of years ago, a tribe of man-apes is driven from their water hole by a rival tribe. They wake to find a featureless black monolith has appeared before them. One man-ape realizes how to use a bone as a tool and weapon; the tribe kills the leader of their rivals and reclaims the water hole. Millions of years later, a Pan Am space plane carries Dr. Heywood R. Floyd to a space station orbiting Earth for a layover on his trip to Clavius Base, a United States outpost on the moon. After a videophone call with his daughter, Floyd’s Soviet scientist friend and her colleague ask him about rumors of a mysterious epidemic at Clavius. Floyd declines to answer. At Clavius, Floyd heads a meeting of base personnel, apologizing for the epidemic cover story but stressing secrecy. His mission is to investigate a recently found artifact buried four million years ago. Floyd and others ride in a Moonbus to the artifact, which is a monolith identical to the one encountered by the man-apes. Sunlight strikes the monolith and a loud high-pitched radio signal is heard. Eighteen months later, the U.S. spacecraft Discovery One is bound for Jupiter. On board are mission pilots and scientists Dr. David Bowman and Dr. Frank Poole with three other scientists in cryogenic hibernation. Most of Discovery’s operations are controlled by the ship’s computer, HAL 9000, referred to by the crew as “Hal”. Bowman and Poole watch Hal and themselves being interviewed on a BBC show about the mission, in which the computer states that he is “foolproof and incapable of error.” When asked by the host if Hal has genuine emotions, Bowman replies that he appears to, but that the truth is unknown. Later, Hal questions Dave on the mysterious purpose of the mission, then reports the imminent failure of an antenna control device. The astronauts retrieve the component making use of an EVA Pod but find nothing wrong with it. Hal suggests reinstalling the part and letting it fail so the problem can be found. Mission Control advises the astronauts that results from their twin HAL 9000 backups indicate that Hal is in error. Hal insists that the problem, like previous issues ascribed to HAL series units, is due to human error. Concerned about Hal’s behavior, Bowman and Poole enter an EVA pod to talk without Hal overhearing, and agree to disconnect Hal if he is proven wrong. Hal secretly follows their conversation by lip reading. While Poole attempts to replace the unit during a space walk, his EVA pod, controlled by Hal, rams him, severing his oxygen hose and setting him adrift. Bowman takes another pod to attempt rescue, leaving his helmet behind. Meanwhile Hal turns off the life support functions of the crewmen in suspended animation. When Bowman returns to the ship with Poole’s body, Hal refuses to let him in, stating that the astronauts’ plan to deactivate him jeopardizes the mission. Bowman opens the ship’s emergency airlock manually, enters the ship, and proceeds to Hal’s processor core. Hal tries to reassure Bowman, then pleads with him to stop, and finally expresses fear. As Bowman deactivates the circuits controlling HAL’s higher intellectual functions, HAL regresses to his earliest programmed memory, the song “Daisy Bell”, which he sings for Bowman. When Hal is finally disconnected, a pre-recorded video message from Floyd reveals the existence of the monolith on the moon; its purpose and origin unknown. With the exception of one short, but extremely powerful radio emission aimed at Jupiter, the object has been inert. At Jupiter, Bowman leaves Discovery One in an EVA pod to investigate another monolith discovered in orbit around the planet. The pod is pulled into a vortex of colored light, and Bowman races across vast distances of space, viewing bizarre cosmological phenomena and strange landscapes of unusual colors. He finds himself, still in the pod, in a bedroom appointed in the neoclassical style. He sees older versions of himself, his point of view switching each time, first standing in the bedroom, middle-aged, and still in his spacesuit, then formally dressed and eating dinner, and finally as an old man lying in the bed. A black monolith appears at the foot of the bed, and as Bowman reaches for it, he is transformed into a fetus enclosed in a transparent orb of light. The film ends as the new being floats in space beside the Earth, gazing at it.
整个故事开始於地球上居住的原始的猿猴。它们因为某個巨大的黑石板產生的進化，並因此而懂得并使用工具來狩獵動物。随后，故事来到了人類科技已有能 力能夠運送自己到月球去的時候。美国的月球基地发现了相同的黑石板，由于黑石板明显为非自然产物，当局决定对此发现严格保密，月球基地因此有新型传染病的 流言，而与此同时科学家开始对黑石板进行研究。他們發現這塊黑石板是一個發射器，因為它發出了一种尖銳的訊號，射向木星。 18個月之後，一艘發現號太空船被委派到木星調查訊號的終點。太空船上的人員包括大衛·鮑曼博士, 法蘭克·普爾，和一台先進且具有 人工智慧超智慧電腦HAL 9000來控制整艘太空船。此外，太空船上还有三位處於冬眠狀態科學家。但是遠航之旅逐漸變為可怕的旅行，超智慧電腦HAL發現大衛·鮑曼與法蘭克·普爾打算將他的主機關閉。對超智慧電腦來說，关闭它的主机將殺死它，所以超智慧電腦決定先發制人，殺害三位冬眠狀態科學家及用製造假故障的狀況，讓法蘭克·普爾去太空船外修理，然后用HAL的小型艇將法蘭克·普爾的氧氣剪斷，導致法蘭克·普爾缺氧而死。而唯一倖存者大衛·鮑曼在設法關閉HAL電腦的同時，到達木星。此時大衛·鮑曼發現一個更大的黑石板出現在軌道上。 當他去調查石板時，不自主被傳送到無限遠的地方。許久之後，大衛·鮑曼發現小艇已停在一間佈置華麗的房間裡。突然大衛·鮑曼發現到自己正以極快的速度老去，在躺在床上老死之前，他看見巨大第四塊石板出現在面前，而他也轉變成婴孩一般，飄浮在宇宙中凝望著數之不盡的星星。