The standard published edition of J.R.R. Tolkien’s The Lord of the Rings is made up of three volumes.
The volumes are The Fellowship of the Ring, The Two Towers, and The Return of the King. Tolkien conceived the work as a single long novel, but paper shortages and publishing decisions led it to appear in three separate volumes between 1954 and 1955.
The story itself is divided internally into six books, plus appendices, so “three” refers to the usual publication format rather than the novel’s internal structure. The trilogy label is therefore convenient but can be misleading: Tolkien did not originally describe the work as three independent novels.