The Oscar-winning actor, 50, was particularly thrilled to learn he'd be playing a villain whom audiences can't help but root for in the end.
"Everybody knows what they want and is out for certain selfish acts and deeds in this film, and I think for wrong or for right, hook or by crook, whether they're doing despicable things or not, there's a sort of envy of going wow to be that self-assured in what you want and to go after it and to die for it, you know, however it is, there's something fun about that," he told Fox News.
"This is what Guy does in this milieu, this is what he does with 'Lock, Stock' and 'Snatch' and this. You know, it's gonna be action-packed whodunit but dark comedy," McConaughey added.
A strong ensemble cast -- including Charlie Hunnam, Henry Golding, Michelle Dockery, Jeremy Strong, Colin Farrell and Hugh Grant -- rounds out this high-stakes story that centers on McConaughey's character's profitable marijuana empire in London and others' attempts to take it over.
Dockery said Ritchie's storytelling style kept her on her toes because he's known for rewriting scenes at the last minute and handing actors new pages in their makeup trailers.
Another draw for audiences? The movie's high street English fashion makes these complicated characters pop on screen.
"I loved my suits, but I got to wear them. And I still have them," McConaughey admitted.
Golding added: "I didn't spend any time on set with the Sweeney toddlers [Farrell's character] but those outfits were insane... and I foresee bachelor parties in the U.K. never being the same again."
The film hits theaters on Jan. 24.