The Gas Heart or The Gas-Operated Heart (French: Le Cœur à gaz) is a French-language play by Romanian-born author Tristan Tzara. It was written as a series of non sequiturs and a parody of classical drama—it has three acts despite being short enough to qualify as a one-act play. A part-musical performance that features ballet numbers, it is one of the most recognizable plays inspired by the anti-establishment trend known as Dadaism. The Gas Heart was first staged in Paris, as part of the 1921 "Dada Salon" at the Galerie Montaigne.

The play's second staging, as part of the 1923 show Le Cœur à barbe ("The Bearded Heart") and connected to an art manifesto of the same name as the latter, featured characteristic costumes designed by Sonia Delaunay. The show coincided with a major split in the avant-garde movement, which, in 1924, led Tzara's rivals to establish Surrealism. Opposing his principles to the dissident wing of Dada, represented by André Breton and Francis Picabia, Tzara rallied around him a group of modernist intellectuals, who endorsed his art manifesto. The conflict between Tzara and Breton culminated in a riot, which took place during the premiere of The Gas Heart.

In The Gas Heart, Tzara appears to have aimed at overturning theatrical tradition, in particular the three-act play, which resulted in the suggestion that the text is "the greatest three-act hoax of the century". American literary historian David Graver, who compares The Gas Heart with Le Serin muet, a play by Tzara's friend Georges Ribemont-Dessaignes, notes of the two texts that, together, they "pulverize the elements of conventional theater they use so finely that few gestures or remarks cohere in any recognizable order. These manifestations of dada at its most extreme reduce theatrical spectacle to a kind of white sound, the significance of which depends almost exclusively upon the cultural context in which it is presented."

Tristan Tzara himself offered insight into the satirical and subversive intent of The Gas Heart, writing: "I beg my interpreters to treat this play as they would a masterpiece like Macbeth, but to treat the author, who's no genius, without any respect [...]" Tzara, whose own definition of the text described it as "a hoax", suggested that it would "satisfy only industrialized imbeciles who believe in men of genius", and argued that it offered "no technical innovation".

The play takes the form of an absurd dialogue between characters named after human body parts: Mouth, Ear, Eye, Nose, Neck, and Eyebrow. The entire exchange between them uses and reinterprets metaphors, proverbs and idiomatic speech, suggesting the generic roles traditionally assigned by folklore to the body parts in question, rather than situations involving the characters themselves, with lines uttered in such manner as to make the protagonists look obsessed. In one such example of a non sequitur, Ear says: "The eye tells the mouth: open your mouth for the candy of the eye." It is probable that such exchanges between Eye and Mouth are a form of courtship, a matter which, according to theater critic Peter Nichols, may help one understand why some of the exchanges in the background turn from nonsensical to "a more lyrical expression of desire." This situation, Nichols proposes, may also explain the title of the play, a probable allusion to "the power of love as a kind of life-force".

In addition to this motif, the play features a series of seemingly metaphysical observations, which characters make about themselves or about unspecified third parties. For example, Mouth states: "Everyone does not know me. I am alone here in my wardrobe and the mirror is blank when I look at myself." Another such line reads: "The void drinks the void: air was born with blue eyes, that's why it endlessly swallows aspirin." One other exchange, in which Ear compares herself to a "prize horse", results later in the text in an actual metamorphosis, through which she becomes the horse Clytemnestra (named after the femme fatale character in Greek myths).

A series of dance routines, described by British theater historian Claude Schumacher as "bewildering ballets", accompanies the dialogues. In its third act, The Gas Heart also features a dance performed by a man fallen from a funnel, which, American critic Enoch Brater argues, shares characteristics with Alfred Jarry's ubuesque situations. Critic Michael Corvin also notes that the position of characters as specified by Tzara, alternating between an extreme height above the audience or episodes of collapsing on the stage, is a clue to how the protagonists relate to one another, and in particular to the tribulations of their love affairs. For both the third act and the play itself, Tzara's original text culminates in doodles, which alternate the various spellings of a group of letters with drawings of hearts pierced by arrows. According to Brater: "Here the dramatic genre seems to have broken down completely."

The Gas Heart was first staged as part of a Dada Salon at the Galerie Montaigne by the Paris Dadaists on June 6, 1921. The cast included major figures of the Dada current: Tzara himself played the Eyebrow, with Philippe Soupault as the Ear, Théodore Fraenkel as the Nose, Benjamin Péret as the Neck, Louis Aragon as the Eye, and Georges Ribemont-Dessaignes as the Mouth. The production was received with howls of derision and the audience began to leave while the performance was still in progress.