And the excitement does not end there.
News broke back in May that Gyllenhaal had been tapped to play villain Mysterio in the new Spider-Man film, but both Marvel and the actor himself have been quiet on that - until now.
Even though plot details surrounding the movie are being kept under wraps, Mysterio has appeared in several Spider-Man cartoons and video games.
In his first ever post, he can be seen reading "The Amazing Spider-Man" comic book.
You may recall that way back when Tobey Maguire was playing Spidey and almost bowed out due to a back injury, Gyllenhaal was rumored to be taking over the webslinger's suit.
Gyllenhaal had been rumoured to be in the film and confirmed the news on Instagram on Wednesday.
Spider-Man: Far From Home is the sequel to Spider-Man: Homecoming, the first solo outing for Tom Holland's version of the character.
This may be a playful nod to that brief period in 2003 when Tobey Maguire was trying to get a bigger payday for Sam Raimi's Spider-Man 2, and Sony called his bluff to the point where the studio actually met with Gyllenhaal as a possible replacement.
In the comics, Mysterio is Quentin Beck, a special effects technician who uses his tech wizardry to become a master criminal, leading to him butting heads - or his fish-bowl helmet - with Spidey.