To Catch a Killer is a two-part television film from 1992, directed by Eric Till and starring Brian Dennehy and Michael Riley.

As he investigates the missing person report of a teenager named Christopher Gant (based on Gacy's final victim, Robert Piest), Des Plaines, IL detective Lt. Joseph R. Kozenczak (Riley) becomes concerned that local businessman John Wayne Gacy (Dennehy) may be responsible for this as well as many other disappearances.

The film broadly follows the historical narrative of the investigation which led to John Wayne Gacy's arrest in December 1978 and it does not directly depict his earlier life or his criminal activity prior to 1978.

These changes were probably made for legal reasons, because many key witnesses and victims' family members, as well as Gacy himself, were still alive at the time of the film's production.

In 2010, eighteen years after the film's first broadcast in the US and sixteen years after John Wayne Gacy's execution, a profile of Dennehy in Times of North West Indiana noted, "whenever Dennehy comes back to Chicago, which is often ... he's inevitably asked about his made-for-television 1992 movie role in To Catch a Killer.