The 37-year-old actor, who was already on Facebook, debuted on the photo-and-video-sharing app Instagram on Wednesday.
Gyllenhaal shared a video promoting Mysterio, his character from the upcoming film Spider-Man: Far From Home, which will see Tom Holland reprising his role of the titular web slinger.
The Oscar-nominated actor captioned his first post: "I just realised I'm not playing Spider-Man."
The funny clip opens with Gyllenhaal reading an Amazing Spider-Man comic, titled 'The Return Of The Man Called Mysterio' and exclaiming, "Whoa! What the f**k?"
Mysterio is the antagonist in the follow-up to the 2017's Spider-Man: Homecoming.
Gyllenhaal already has over 268k followers and is following 39 people on the social media app.
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