Douglas Alexander Smith is a Canadian actor known for his work on the HBO series Big Love as Ben Henrickson.

His other work includes Percy Jackson: Sea of Monsters (2013), Terminator Genisys (2015), Vinyl, Miss Sloane (both 2016), When We Rise (2017), The Alienist (2018–2020) and the second season of HBO's Big Little Lies (2019).

An alumnus of RADA's Shakespeare Summer School, Smith made his off-Broadway debut in 2014, starring in the New York premiere of Simon Stephens' Punk Rock at the Lucille Lortel Theatre in the West Village.

David Rooney of The Hollywood Reporter wrote, "In such an exemplary cast, it's unfair to single out any one of the seven principal actors for special praise.

His turn as one half of the darkly comedic Isaacson duo earned praise from critics like David Nevins of The Guardian who, in his review of the show, wrote: "Two of the best performances, though, are those of Matthew Shear and Douglas Smith as the brothers Isaacson, two bright and innovative Jewish forensic science specialists who stick out like sore thumbs in the very Irish-Catholic environs of Manhattan law enforcement.

"[7] In 2019, Smith played an integral role in the second season of HBO's Big Little Lies as Corey Brockfield, a co-worker and love interest of main character Jane Chapman.

[8] He plays a supporting role in Kevin Costner's Horizon: An American Saga – Chapter 1 which premiered at the 2024 Cannes Film Festival.