Leigh Whannell (/ˈli wɑːˈnɛl/; born 17 January 1977) is an Australian filmmaker and actor. He has written multiple films that were directed by his friend James Wan, including Saw (2004), Dead Silence (2007), Insidious (2010), and Insidious: Chapter 2 (2013). Whannell made his directorial debut with Insidious: Chapter 3 (2015), and has since directed three more films: Upgrade (2018), The Invisible Man (2020), and Wolf Man (2025).

Whannell and Wan are the creators of the Saw franchise. Whannell wrote the first installment, co-wrote the second and third installments, was producer or executive producer for all the films, and appeared as the Adam Stanheight character in three of the installments. He was also the writer of the Saw video game (2009), and co-writer of the 2014 film Cooties.

Whannell was born 17 January 1977.

A writer since childhood, Whannell worked as a reporter and film critic for several Australian television shows, including ABC's Recovery, a Saturday morning youth-oriented program that was hosted by Dylan Lewis. Whannell has described the show in a 2011 blog post:

The result was that instead of following the usual MTV ideal of what teenagers want in a TV show—"Hey kids, coming up next we’ve got some seriously WICKED windsurfing moves!!”—Recovery managed to tap into the so-called "alternative" movement that was in full swing at the time by giving teenagers what they actually want: genuine, unpolished anarchy.

Whannell had originally auditioned for the host role, but was later employed as a reporter; Whannell's first interview was with Jackie Chan and he has stated that "Recovery is the best job I've ever had ...".

Whannell appeared in Episode 4, Season 1 of the RMITV production Under Melbourne Tonight presents What's Goin' On There? on 10 June 1998.

In 2003, Whannell appeared in a minor role in The Matrix Reloaded, as well as in the video game Enter The Matrix as the character "Axel".