The theme of alienation is central to The Stranger. Meursault, the protagonist, experiences profound detachment from society and its norms. His indifference to social conventions and emotional events highlights his isolation. This alienation is not just personal but also reflects broader existential themes, questioning the meaning and significance of life.

Meursault's alienation is evident from the beginning, as he shows no emotion at his mother's funeral. His lack of grief and emotional response alienate him from others, who expect a display of sorrow. The vigil scene illustrates this disconnect:

I inclined to think that they were greeting me, after their fashion, but it had a queer effect, seeing all those old fellows grouped round the keeper, solemnly eying me and dandling their heads from side to side. For a moment I had an absurd impression that they had come to sit in judgment on me.

This perception of judgment underscores his feeling of being an outsider.

Meursault's trial further amplifies his alienation. His unemotional demeanor and lack of belief in God are incomprehensible to the magistrate and society, deepening his isolation. Ultimately, he embraces his alienation, accepting the absurdity of life. In the novel's final lines, he finds a sense of peace in his solitude:

To feel it so like myself, indeed, so brotherly, made me realize that I’d been happy, and that I was happy still. For all to be accomplished, for me to feel less lonely, all that remained to hope was that on the day of my execution there should be a huge crowd of spectators and that they should greet me with howls of execration.

This acceptance of alienation reflects his existential realization.

The setting of Algeria, with its cultural and social tensions, reinforces Meursault's alienation. As a Frenchman in a colonized land, he is already an outsider. The cultural clash between French and Arab customs further isolates him. The novel's title, L’Étranger, meaning "The Stranger," "The Outsider," or "The Alien," underscores this theme. In a land where no one truly belongs, Meursault's alienation is both personal and universal.