One of the three off-shoot campaign settings to Forgotten Realms, alongside Kara-Tur and Al-Qadim. Like its counterparts, it focuses on an "ethnically different" area of the Toril world - in this specific case, a South America expy, in contrast to the Arabic Al-Qadim and the "Oriental" Kara-Tur.

Noted for being pretty well researched, for the time, but quite shamelessly ripped wholesale from the actual lore and history of South America, complete with the invasion of Conquistador-expies (a Helm-worshipping legion of mercenaries) who commit such brutal atrocities against the natives that Helm has to found a whole new Paladin order to try and make up for the shit they did.

After Tomb of Annihilation was released, Maztica became legal to post content for on the DM's Guild. A fan group has made a huge translation of the setting to Dungeons & Dragons 5th Edition... as to whether it manages to be something more than "South America ported wholesale to the Realms", well...

Dungeons & Dragons Campaign Settings
Basic D&D: Mystara (Blackmoor) - Pelinore
AD&D: Birthright - Council of Wyrms - Dark Sun - Dragonlance
Forgotten Realms (Al-Qadim - The Horde - Icewind Dale - Kara-Tur - Maztica)
Greyhawk - Jakandor - Mystara (Hollow World - Red Steel - Savage Coast)
Planescape - Ravenloft (Masque of the Red Death) - Spelljammer
3rd/3.5 Edition: Blackmoor - Dragonlance - Eberron - Forgotten Realms
Ghostwalk - Greyhawk (Sundered Empire)
Ravenloft (Masque of the Red Death) - Rokugan
4th Edition: Blackmoor - Dark Sun - Eberron - Forgotten Realms - Nentir Vale
5th Edition: Eberron - Exandria - Forgotten Realms - Greyhawk - Ravenloft - Ravnica - Theros
Third Party: Askis (5E) - Arkadia (5E) - Dragonmech (3E) - Dragonstar (3E) - Golarion (3E)
Humblewood (5E) - Kingdoms of Kalamar (2E/3E/4E) - Midgard (3E/4E/5E)
Midnight (3E/4E) - Mists of Akuma (5E) - Odyssey (5E) - Primeval Thule (5E)
Ptolus (3E/5E) - Rokugan (3E) - Scarred Lands (3E/5E) - Spellslinger (3E)
Wilderlands of High Fantasy (Basic/3E) - World of Farland (3E/4E/5E)