Knox Harrington is a video artist possibly involved in a romantic relationship with Maude Lebowski. Not much is known about him and he appears in only one scene in the film. He is played by David Thewlis.
Harrington is sitting in a chair in Maude's studio loft when The Dude makes his second visit to talk to Maude. Knox seems indifferent to The Dude, leafing through a magazine while engaging in small talk. The Dude seems somewhat put off by Harrington's snobby attitude. When The Dude asks who he is, Harrington curtly replies "Just a friend of Maudie's".
Harrington himself is British and has a twittering laugh. When he answers the phone for Maude, he and Maude have a conversation in Italian with an unseen and unheard man named Sandro in which they erupt into fits of laughter, leaving The Dude standing between them confused.