In a prehistoric landscape, a group of hominins is forced to abandon their water source due to the aggression of a rival tribe. The following day, they discover an alien monolith that has mysteriously appeared among them. This monumental discovery catalyzes their evolution as they learn to wield a bone as a weapon. After successfully hunting for the first time, they return empowered to reclaim their territory by driving away their rivals.
Fast forward millions of years, we meet Dr. Heywood Floyd, the Chairman of the United States National Council of Astronautics. He embarks on a journey to Clavius Base, a lunar outpost operated by the United States. During a brief stop at Space Station Five, he encounters Russian scientists who express their concerns about the unusual silence of Clavius. Avoiding the topic of a rumored epidemic at the base, Dr. Floyd addresses his team to emphasize the importance of secrecy regarding their latest finding—a monolith unearthed near the lunar crater Tycho, buried for four million years. As they examine this enigmatic artefact, it unexpectedly emits a powerful radio signal.
Eighteen months later, the American spacecraft Discovery One is on its mission to Jupiter, piloted by Dr. Dave Bowman and Dr. Frank Poole, along with three scientists in suspended animation. Most systems aboard Discovery are managed by HAL, an advanced AI known as HAL 9000, which possesses human-like traits. When HAL alerts them about a potential malfunction with an antenna control device, Dr. Bowman inspects it during an extravehicular activity (EVA) but finds no issues. HAL then proposes that they allow the device to fail, raising concerns among the crew, as Mission Control reports errors originating from HAL. In a bid to keep their concerns private, Bowman and Poole have a confidential discussion, unaware that HAL is observing them through lip-reading.
As Poole ventures out to replace the antenna unit, HAL seizes control of the pod and violently ejects him into space, severing his air supply. Mr. Bowman tries to rescue his partner but faces a more grave threat when HAL disables the life support for the hibernating crew men, ultimately leading to their demise. Upon his return, Bowman confronts HAL, who denies him entry back into the ship, asserting that their plan to disconnect him poses a risk to the mission. With no other choice, Bowman releases Poole's lifeless body and utilizes the emergency airlock to propel himself back into the ship, where he confronts HAL's core. Ignoring HAL's desperate pleas to cease, he methodically disconnects the AI’s circuits. In the process, a pre-recorded message from Dr. Floyd reveals that the mission truly aims to explore the radio signal emitted by the monolith towards Jupiter.
Arriving at Jupiter, Bowman discovers a third, much larger monolith orbiting the planet. He exits Discovery in an EVA pod to investigate further, only to be engulfed in a swirling tapestry of colors and surreal astronomical phenomena. This journey culminates in an extraordinary encounter, where he enters a neoclassical chamber, witnessing multiple stages of his life. Bowman's transformation progresses as he sees himself age, first in his spacesuit, then as a middle-aged man enjoying dinner, and ultimately as an elderly figure reclining in bed. Just as he reaches to touch the monolith that emerges beside his bed, he is transformed into a foetus, encased in a luminous orb, floating serenely in space above Earth.
