Gensomaden Saiyuki (幻想魔伝 最遊記, Gensōmaden Saiyūki?), commonly known as Saiyuki, is a popular manga series created by Kazuya Minekura. The story is loosely based on the famous Chinese novel Journey to the West (Xīyóu Jì). In 1999 the Saiyuki OVA by Tokyo Kids was released. A year later it was adapted into an anime series by Studio Pierrot. The Gensomaden Saiyuki: Requiem movie appeared in theaters in Japan in 2001. A sequel to this movie is the Gensomaden Saiyuki: Kibou no zaika OVA, which is actually animation taken from an interactive game

There are two sequels to Saiyuki, Saiyuki Reload (最遊記RELOAD, Saiyuki Reload?), a manga sequel adapted into an anime, and Saiyuki Reload Gunlock (最遊記RELOAD GUNLOCK, Saiyuki Reload Gunlock?), an anime sequel. Saiyuki Gaiden is a manga prequel which had a few chapters adapted into the original anime.

Source: Wikipedia