'The Intentional Fallacy' by W.K. Wimsatt and Monroe C.Beardsley.
Just to add to the answer already posted here, I will say one to words. 'Intentional fallacy' as a critical term derives its importance from the fact that it makes the reading of authorial intention as a fallacy, on the part of the literary critic.
The American New Criticism and the subsequent development of I.A.Richards's 'practical criticism'---all of this takes the cue from the Modernist cult of impersonality, as set forth by T.S.Eliot in his famous essay 'Tradition and the Individual Talent'. These critical turns shifts the emphasis from the author to the text and the kinds of meaning it can generate independent of its author.
This questioning of 'one' authorial intention as some kind of sovereign 'one' meaning of the text is something looks forward to Roland Barthes and Michel Foucault's interrogation of the authorial identity in later criticism in the second half of the twentieth century.
In 1946 W.K. Wimsatt and Monroe C. Beardsley published an essay entitled "The Intentional Fallacy." The word 'fallacy' means 'a false way of reasoning' or 'an invalid mode of reasoning.' They argued that it is wrong to base a critical judgement regarding the meaning or the value of a poem on external evidence like the intention of the author. They asserted that a poem should be studied and judged for its own sake and not for anything else. They asserted that once the poet has written his poem it ceases to belong to him, and his intentions in writing that poem should not be taken into consideration when judging it.
Their essay became the cornerstone of a new school of criticism which came to be known as "New Criticism."