Dr. Lanyon is a somewhat minor character in The Strange Case of Dr. Jekyll and Mr. Hyde by Robert Louis Stevenson, but important to the progress of the narrative. He is a close friend of both Gabriel John Utterson and of Dr. Jekyll, but is medically conservative and disapproves of Dr. Jekyll's experiments. As Mr. Utterson strives to solve the mystery of Hyde, he approaches Lanyon, but Lanyon at first prevaricates. When Dr. Jekyll accuses Lanyon of being a "hide-bound pedant", this makes Utterson think that their falling out was merely over a point of science. As we discover later in the story, after the death of Lanyon, Lanyon helped Jekyll by bringing him the potion that turned him back from Hyde into Jekyll but disapproves of Jekyll's work.
Lanyon is not a particularly well-rounded character in the story. In contrast to both Jekyll and Utterson, he is intended to represent an ordinary, rather conventional person appalled by Jekyll's experiments. He seems pleasant, responsible, and kind, willing to help out an old friend, but otherwise is not really presented in detail but merely acts as a vehicle for the plot.