Which comic-book publisher introduced the character Judge Dredd in 2000 AD?

The comic-book publisher that introduced Judge Dredd in 2000 AD was IPC Magazines.

Judge Dredd first appeared in the British science-fiction comic anthology 2000 AD in 1977. The character was created by writer John Wagner and artist Carlos Ezquerra, with early development also involving writer Pat Mills. IPC Magazines published 2000 AD at the time, so it was the original publisher associated with Dredd’s debut.

Judge Dredd is a law-enforcement officer in the dystopian Mega-City One, where judges act as police, courts, and executioners. The stories use exaggerated authoritarian justice to satirize politics, policing, media, and American-style urban excess. Dredd’s identity is deliberately impersonal: he rarely removes his helmet, allowing the uniform to represent the system.

2000 AD later became associated with Fleetway and Rebellion developments, which can make the original publisher difficult to identify. Marvel and DC published unrelated superhero material, while Image Comics did not introduce Judge Dredd.