Since its premiere in 1968, the film 2001: A Space Odyssey has been analysed and interpreted by numerous people, ranging from professional film critics to amateur writers and science fiction fans. The director of the film, Stanley Kubrick, and the writer, Arthur C. Clarke, wanted to leave the film open to philosophical and allegorical interpretation, purposely presenting the final sequences of the film without the underlying thread being apparent; a concept illustrated by the final shot of the film, which contains the image of the embryonic "Starchild". Nonetheless, in July 2018, Kubrick's interpretation of the ending scene was presented after being newly found in an early interview.

Openness to interpretation Kubrick encouraged people to explore their own interpretations of the film, and refused to explain "what really happened" in the movie, preferring instead to let audiences embrace their own ideas and theories. In a 1968 interview with Playboy, Kubrick stated:

Neither of the two creators equated openness to interpretation with meaninglessness, although it might seem that Clarke implied as much when he stated, shortly after the film's release, "If anyone understands it on the first viewing, we've failed in our intention." When told of the comment, Kubrick said "I believe he made it [the comment] facetiously. The very nature of the visual experience in 2001 is to give the viewer an instantaneous, visceral reaction that does not—and should not—require further amplification." When told that Kubrick had called his comment 'facetious', Clarke responded

In a subsequent discussion of the film with Joseph Gelmis, Kubrick said his main aim was to avoid "intellectual verbalization" and reach "the viewer's subconscious". He said he did not deliberately strive for ambiguity, that it was simply an inevitable outcome of making the film non-verbal, though he acknowledged that this ambiguity was an invaluable asset to the film. He was willing then to give a fairly straightforward explanation of the plot on what he called the "simplest level", but unwilling to discuss the metaphysical interpretation of the film which he felt should be left up to the individual viewer."The Film Director as Superstar" (Doubleday and Company: Garden City, New York, 1970) by Joseph Gelmis.

Clarke's novel as explanation Arthur C. Clarke's novel of the same name was developed simultaneously with the film, though published after the film's release.Arthur C. Clarke, The Lost Worlds of 2001. London: Sidgwick and Jackson, 1972. It seems to explain the ending of the film more clearly. Clarke's novel explicitly identifies the monolith as a tool created by extraterrestrials that have been through many stages of evolution, moving from organic forms, through biomechanics, and finally to a state of pure energy. The book explains the monolith much more specifically than the movie, depicting the first (on Earth) as a device capable of inducing a higher level of consciousness by directly interacting with the brain of pre-humans approaching it, the second (on the Moon) as an alarm signal designed to alert its creators that humanity had reached a sufficient technological level for space travel, and the third (near Jupiter in the movie but on a satellite of Saturn in the novel) as a gateway or portal to allow travel to other parts of the galaxy. It depicts Bowman traveling through some kind of interstellar switching station which the book refers to as "Grand Central," in which travelers go into a central hub and then are routed to their individual destinations. The book also depicts a crucial utterance by Bowman when he enters the portal via the monolith; his last statement is "my God!—it's full of stars!" This statement is not shown in the movie, but becomes crucial in the 1984 sequel 2010: The Year We Make Contact, based on the novel 2010: Odyssey Two.

The book reveals that these aliens travel the cosmos assisting lesser species to take evolutionary steps. Bowman explores the hotel room methodically, and deduces that it is a kind of zoo created by aliens—fabricated from information derived from television transmissions from Earth intercepted by the TMA-1 monolith—in which he is being studied by the invisible alien entities. He examines some food items provided for him, and notes that they are edible, yet clearly not made of any familiar substance from Earth. Kubrick's film leaves all this unstated. Although not included in the movie, Kubrick did originally plan to have aliens portrayed in the movie, and only cut the idea after deciding that it was too hard to do it with special and practical effects.

Physicist Freeman Dyson urged those baffled by the film to read Clarke's novel:

Clarke himself used to recommend reading the book, saying "I always used to tell people, 'Read the book, see the film, and repeat the dose as often as necessary'", although, as his biographer Neil McAleer points out, he was promoting sales of his book at the time. Elsewhere he said, "You will find my interpretation in the novel; it is not necessarily Kubrick's. Nor is his necessarily the 'right' one – whatever that means."

Film critic Penelope Houston noted in 1971 that the novel differs in many key respects from the film, and as such, it perhaps should not be regarded as the skeleton key to unlock it.

Stanley Kubrick was less inclined to cite the book as a definitive interpretation of the film, but he also frequently refused to discuss any possible deeper meanings during interviews. During an interview with Joseph Gelmis in 1969, Kubrick explained:

Author Vincent LoBrutto, in Stanley Kubrick: A Biography, was inclined to note creative differences leading to a separation of meaning for book and film:

Religious interpretations

In an interview for Rolling Stone magazine, Kubrick said "On the deepest psychological level the film's plot symbolizes the search for God, and it finally postulates what is little less than a scientific definition of God . . . The film revolves around this metaphysical conception, and the realistic hardware and the documentary feelings about everything were necessary in order to undermine your built-in resistance to the poetical concept."

When asked by Eric Nordern in Kubrick's interview with Playboy if 2001: A Space Odyssey was a religious film, Kubrick elaborated:The ALT.MOVIES.KUBRICK FAQ. Extract: What did Kubrick have to say about what 2001 "means"? I will say that the God concept is at the heart of 2001 but not any traditional, anthropomorphic image of God. I don't believe in any of Earth's monotheistic religions, but I do believe that one can construct an intriguing scientific definition of God, once you accept the fact that there are approximately 100 billion stars in our galaxy alone, that each star is a life-giving sun and that there are approximately 100 billion galaxies in just the visible universe. Given a planet in a stable orbit, not too hot and not too cold, and given a few billion years of chance chemical reactions created by the interaction of a sun's energy on the planet's chemicals, it's fairly certain that life in one form or another will eventually emerge. It's reasonable to assume that there must be, in fact, countless billions of such planets where biological life has arisen, and the odds of some proportion of such life developing intelligence are high. Now, the Sun is by no means an old star, and its planets are mere children in cosmic age, so it seems likely that there are billions of planets in the universe not only where intelligent life is on a lower scale than man but other billions where it is approximately equal and others still where it is hundreds of thousands of millions of years in advance of us. When you think of the giant technological strides that man has made in a few millennia—less than a microsecond in the chronology of the universe—can you imagine the evolutionary development that much older life forms have taken? They may have progressed from biological species, which are fragile shells for the mind at best, into immortal machine entities—and then, over innumerable eons, they could emerge from the chrysalis of matter transformed into beings of pure energy and spirit. Their potentialities would be limitless and their intelligence ungraspable by humans.

In the same interview, he also blames the poor critical reaction to 2001 as follows: Perhaps there is a certain element of the lumpen literati that is so dogmatically atheist and materialist and Earth-bound that it finds the grandeur of space and the myriad mysteries of cosmic intelligence anathema.

In a 1980 interview that remained obscure until being rediscovered in 2018, Kubrick explained the intent of the film's ending. God-like beings of "pure energy and intelligence" place the astronaut in a human zoo, where he passes his entire life with "no sense of time". After they eventually finish with him, he is "transformed into some kind of super being and sent back to Earth, transformed and made into some sort of superman ... It is the pattern of a great deal of mythology, and that is what we were trying to suggest."

Allegorical interpretations

The film has been seen by many people not only as a literal story about evolution and space adventures, but as an allegorical representation of aspects of philosophical, religious or literary concepts.

Nietzsche allegory Friedrich Nietzsche's philosophical tract Thus Spoke Zarathustra, about the potential of mankind, is directly referred to by the use of Richard Strauss's musical piece of the same name. Nietzsche writes that man is a bridge between the ape and the Übermensch. In an interview in The New York Times, Kubrick gave credence to interpretations of 2001 based on Zarathustra when he said: "Somebody said man is the missing link between primitive apes and civilized human beings. You might say that is inherent in the story too. We are semicivilized, capable of cooperation and affection, but needing some sort of transfiguration into a higher form of life. Man is really in a very unstable condition." Moreover, in the chapter Of the Three Metamorphoses, Nietzsche identifies the child as the last step before the Uberman (after the camel and the lion), lending further support to this interpretation in light of the 'star-child' who appears in the final scenes of the movie.

Nietzsche's Zarathustra includes this passage, which closely describes Bowman blowing the space pod's door by pressing three buttons (two times):

"Thrice did there peal at the gate like thunder, and thrice did the vaults resound and howl again. I pressed the key, then did a roaring wind tear the folds apart: whistling, whizzing, and piercing".

Donald MacGregor has analysed the film in terms of a different work, The Birth of Tragedy, in which Nietzsche refers to the human conflict between the Apollonian and Dionysian modes of being. The Apollonian side of man is rational, scientific, sober, and self-controlled. For Nietzsche a purely Apollonian mode of existence is problematic, since it undercuts the instinctual side of man. The Apollonian man lacks a sense of wholeness, immediacy, and primal joy. It is not good for a culture to be either wholly Apollonian or Dionysian. While the world of the apes at the beginning of 2001 is Dionysian, the world of travel to the Moon is wholly Apollonian, and HAL is an entirely Apollonian entity. Kubrick's film came out just a year before the Woodstock rock festival, a wholly Dionysian affair. MacGregor argues that David Bowman in his transformation has regained his Dionysian side.

Conception allegory