Harbour had relationships with
Alison Sudol and
Julia Stiles. Starting in 2019, he was in a relationship with English singer-songwriter
Lily Allen. They made their red carpet debut during the
26th annual Screen Actors Guild Awards. They married on September 7, 2020, in
Las Vegas in a wedding officiated by an
Elvis impersonator. The couple shared a Brownstone house in Brooklyn and worked with the architect Ben Bischoff. In December 2024,
The Telegraph alleged that Allen and Harbour had separated, after Allen's dating profile was reportedly spotted on the exclusive dating app
Raya. Other reports state that the couple had separated in early 2025. After the release of Allen's fifth studio album
West End Girl, she stated that it was partially based on the "demise" of their relationship and Harbour's alleged infidelity. In an interview with
The Guardian on his role in
Black Widow in July 2021, Harbour said he was a
socialist: "I don't know that there's anyone who could disagree with socialist ideology". He elaborated: "The idea of a kindergarten-type society where we share things is my ideal society—as opposed to this world where we're hunting and killing and destroying for our own personal hoarding, our own personal greed." Harbour struggled with
alcoholism in his past and has been sober since he was 24, after hitting "rock bottom" as he faced homelessness, loneliness and
thoughts of suicide. He began drinking as a teenager and the habit worsened during college. He decided to stop drinking after feeling "very lonely and needing a different direction in my life", and has said, "I enjoy consciousness too much now" to drink again. Harbour enjoys watching
Let's Plays and
speedruns of old video games. Harbour is a fan of the
NHL's
New York Rangers. He is a former believer in the paranormal. ==Filmography==