Final Fantasy XI, also known as Final Fantasy XI Online, is a massively multiplayer online role-playing game (MMORPG), originally developed and published by Squaresoft and then published by Square Enix as the eleventh main installment of the Final Fantasy series. Designed and produced by Hiromichi Tanaka, it was released in Japan on May 16, 2002, for PlayStation 2 and Microsoft Windows-based personal computers in November of that year. The game was the first MMORPG to offer cross-platform play between PlayStation 2 and PC. It was later released for the Xbox 360 in April 2006. All versions of the game require a monthly subscription to play.

Square Co., Ltd. was a Japanese video game development studio and publisher. It was founded in 1986 by Masafumi Miyamoto, who spun off part of his father's electronics company Den-Yu-Sha. Among its early employees were designers Hironobu Sakaguchi, Hiromichi Tanaka, Akitoshi Kawazu and Koichi Ishii, artist Kazuko Shibuya, programmer Nasir Gebelli, and composer Nobuo Uematsu. Initially focusing on action games, the team saw popular success with Final Fantasy in 1987. A role-playing video game, it became the first in a franchise of the same name. Later notable staff included directors Yoshinori Kitase and Takashi Tokita, designer and writer Yasumi Matsuno, artists Tetsuya Nomura and Yusuke Naora, and composers Yoko Shimomura and Masashi Hamauzu.