Arthur Mitchell, often referred to as the "Trinity Killer," is a fictional character and the main antagonist of the fourth season of the Showtime TV series Dexter. Mitchell is a serial killer who presents himself as an unassuming church deacon and family man. FBI agent Frank Lundy dubs him the "Trinity Killer" because of a recurring pattern of three killings based on traumatic events during Arthur's childhood. In the series, Mitchell is portrayed by John Lithgow.

Dexter: New Blood is an American crime drama mystery television series developed for Showtime as a continuation of the series Dexter, developed by original series showrunner, Clyde Phillips, and directed by Marcos Siega. The show features Michael C. Hall and Jennifer Carpenter reprising their roles as Dexter and Debra Morgan, respectively, alongside new cast members Jack Alcott, Julia Jones, Johnny Sequoyah, Alano Miller, and Clancy Brown. The story is set ten years after the events of the original series finale, "Remember the Monsters?", which was broadcast in 2013. It premiered on Showtime on November 7, 2021.