It is well known that Lacan was interested in topology, especially in the 1960s. Yet for all the work he did with topology in his Seminar, it is curious that he never produced a writing dedicated solely to the topic. This paper tries to imagine what an “écrit” on topology by Lacan might have looked like, and what its main points might have been, based on what Lacan says in his Seminar. It then considers why such an écrit was never produced. The answer involves Lacan’s shifting views on psychoanalysis and its relationship to the history of science.