Dexter is an American crime drama series that aired on Showtime from October 1, 2006, to September 22, 2013. Set in Miami, the series centres on Dexter Morgan (Michael C. Hall), a forensic technician specializing in blood spatter analysis for the fictional Miami Metro Police Department, who leads a secret parallel life as a vigilante serial killer, hunting down murderers who have not been adequately punished by the justice system due to corruption or legal technicalities. The show's first season was derived from the novel Darkly Dreaming Dexter (2004), the first in a series of novels by Jeff Lindsay. It was adapted for television by James Manos Jr., who wrote the first episode. Subsequent seasons evolved independently of Lindsay's works while using many of the same characters and concepts.

The series enjoyed mostly positive reviews throughout its run. The first four seasons were widely praised, but reception dropped considerably as the series progressed. The show has received myriad awards, including two Golden Globes won by Hall and John Lithgow for their roles as Dexter Morgan and Arthur Mitchell, respectively. Season four aired its season finale on December 13, 2009, to a record-breaking audience of 2.6 million viewers, making it the most-watched original series episode ever on Showtime at that time.

In April 2013, Showtime announced that season eight would be the final season of Dexter. The season eight premiere was the most watched Dexter episode, with more than 3 million viewers total. The original broadcast of the series finale on September 22, 2013, drew 2.8 million viewers, the largest audience in Showtime's history.

In October 2020, it was announced that Dexter would return with a ten-episode limited series titled Dexter: New Blood, with Hall reprising the title role and Clyde Phillips as showrunner, a position he occupied during the original series' first four seasons. The first season premiered on November 7, 2021, and concluded on January 9, 2022. A continuation of New Blood is in development. In January 2023, a prequel series titled Dexter: Original Sin, was announced as being in development, with Clyde Phillips once again returning as showrunner. This series will follow a younger Dexter as he begins his career with the Miami Metro police department.