"Back on set with my Guardians family for the first day of shooting."
He shared that message with a polaroid picture of the team on set, confirming that the team are back at work and ready to get stuck into the third film.
It's scheduled for release on May 5 2023, so it'll be a while before anything more comes out, but we can at least be safe in the knowledge that they're hard at it from today.
It's been a strange & long & at times challenging journey to get here, but the obstacles along the way have only made this moment more blissful. Back on set with my Guardians family for the first day of shooting #gotgvol3 pic.twitter.com/DrF8ZV8bvz- James Gunn (@JamesGunn) November 8, 2021
The all-star cast includes - as the others have - Chris Pratt, Zoe Saldaña, Dave Bautista, Vin Diesel, Bradley Cooper and Karen Gillan, as well as many more.
So, what do we actually know about the film so far?
Well, Gunn said whilst the second film was being written that he had ideas for the third film, but the Marvel Cinematic Universe has moved on a long way since then.
The events of the third GOTG flick will be set after Avengers: Infinity War and Avengers: Endgame, and - if Gunn is to be believed - will wrap up this particular chapter of the Guardians saga.
Back in 2017, Gunn said: "It will conclude the story of this iteration of the Guardians of the Galaxy, and help catapult both old and new Marvel characters into the next ten years and beyond,
"I will be working side-by-side with Kevin Feige and the gang to help design where these stories go, and make sure the future of the Marvel Cosmic Universe is as special and authentic and magical as what we have created so far."
Gunn himself was later fired from the project after controversial tweets between 2008 and 2012 in which he joked about subjects such as rape and paedophilia emerged.
Whilst he was later reinstated, Gunn said: "I have regretted [those jokes] for many years since.
"Regardless of how much time has passed, I understand and accept the business decisions taken today. Even these many years later, I take full responsibility for the way I conducted myself then.
"All I can do now [is offer] my sincere and heartfelt regret.
"To everyone inside my industry and beyond, I again offer my deepest apologies."
He was later reinstated in 2019, and seems pretty glad to be back in the hotseat for the next instalment.