Dream world

In the Final Fantasy series, Dream Worlds are illusory locations that are distinct from the real worlds, and are generally the manifestations of someone's dreams or wishes.

Final Fantasy III
Unei, Guardian of the Dreamworld, can access the world of dream and summon Dreamworld stones to the real world. While mentioned, the Dreamworld is never visited by the party.

Final Fantasy VI
The Dreamscape is a dream world formed from the mind of Cyan Garamonde as a reflection of his pain for the deaths of his family. It is visited after the Dream Stooges Laragorn, Curlax, and Moebius enter Cyan's soul if the party rests in Doma Castle with Cyan in the World of Ruin. It is also inhabited by Wrexsoul, a demon feeding on Cyan's rage and despair.

Final Fantasy VII
Not strictly speaking a dream world, Cloud's Subconscious is nonetheless a surreal location inside the mind of a comatose Cloud Strife. It is visited by Tifa Lockhart following Cloud and her falling into the Lifestream after Ultimate Weapon's attack on Mideel. Cloud was mentally unstable following the experiments of the Jenova Project, and so has to descend into his own mind to find himself, and Tifa manages to enter his mind thanks to the Lifestream's effects. Since it is Cloud's inner mind, various versions of himself exist as memories from the past.

Final Fantasy IX
When hunting for Chocographs some treasures transport Choco to the Chocobo's Dream World, where he receives new abilities: to cross reefs, mountains, oceans, and finally, the ability to fly. The Fat Chocobo, flanked by a quartet of chocobos of all colors, seems to grant these abilities. Apparently Choco seeks a home and companionship and the abilities given to him will help him find his home; this seems to be a reference to Chocobo's Paradise, which requires Choco's flight ability to reach.

The Dream World can only be accessed by riding Choco and finding one of four special Chocographs, which emit a special gas when discovered. Zidane will fall asleep and Choco will be transported to the Dream World. The following Chocographs grant access to the Dream World: Healing Shore, Dawn Lagoon, Green Plains, and Mist Ocean.

Final Fantasy X
Although not technically a separate world, Dream Zanarkand is a dream copy of the original Zanarkand preserved by the memories of its surviving citizens, whom Yu Yevon turned into fayth and placed on Mt. Gagazet, protected by a dense mist. From their memories Yu Yevon created the Dream Zanarkand and set it far out at sea. To protect himself and his city while he summoned it, Yu Yevon amassed a great amount of pyreflies to form an armor around him; called Sin. Dream Zanarkand is covered by ocean on all sides, and its inhabitants, unaware of being mere dreams of the fayth, believe it to be the entire world. The Dream Zanarkand is preserved in its idealistic state with no war, and thus no summoners, and it's a city of light that never sleeps.

Within Sin also appears to be a dream world of sorts, featuring unnatural architecture and entire landscapes with dream-themed names.

Final Fantasy XI
The Shrouded Land of Dynamis is a parallel dimension separate from Vana'diel, and cannot be entered by normal means. It is a dreamworld created by the terrestrial avatar Diabolos, ruler of dreams, to escape from Vana'diel's fate. The Shadow Lord (known as the Dynamis Lord here), the Dark Kindred, the Forlorn Vanguards, Hydra Corps, and several others were all transported to or entered the realm at some point.

Final Fantasy Tactics Advance
Dream Ivalice is a dream kingdom created by Mewt Randell after he bought the Gran Grimoire from a bookstore. Mewt, his friends and the entire town was brought to this dream kingdom after Mewt uttered some magic words in the Grimoire. It is based on the real Ivalice from the past. Five Crystals hidden in special folds in space maintain this dream world's existence. Laws play an important role in this world, being supervised by the Judges of the palace.