Lu-Tze is a character in the Discworld novels by Terry Pratchett. His name is based on the Taoist philosopherLao Tse.
He first appeared in the novel Small Gods as a minor character. He was one of the History Monks, a member of a Buddhism-like sect, that maintained Discworld history, based on the huge History Books in their Ramtopmonastery. He spent much of the novel in the background, disguised as a simple sweeper. He also deliberately changed the course of history because he didn't like the way things "should" go, replacing a horrific war with a century of peace.
Lu-Tze had a more substantial role in Thief of Time, in which we learn that he is not a monk at all, but "merely" a sweeper at the Monastery of Oi-Dong. In fact, he uses the same trick (that no-one notices a sweeper) in the monastery as he does when out in the world, and has learnt as much about the nature of time as some of the higher monks simply by tidying up the classrooms. Everyone knows Lu-Tze's name, as one of the best monks on the field, but few realise who he actually is.