According to its prologue, the first part of the Prose Tristan (i.e., everything before the Grail material) is attributed to the otherwise unknown Luce de Gast, and was probably written between 1230 and 1235.

[6] The first part of the work stays closer to the traditional story as told by verse writers like Béroul and Thomas of Britain, but many episodes are reworked or altered entirely to fit in the world (and, in the early versions, also the timeline) of the Vulgate Cycle.

The hero Tristan's parents are given new names and backstories, and the overall tone has been called "more realistic" than the verse material though there are moments where characters sing.

Wounded in the fight, he travels to Ireland where he is healed by Iseult, a renowned doctor and Morholt's niece, but he must flee when the Irish discover he has killed their champion.

When they accidentally drink the love potion[8] prepared for Iseult and Mark, they engage in a tragic affair that ends with Tristan being banished to the court of Hoel of Brittany.

Additionally, in the long version, Tristan leaves Brittany and returns to his first love, and never sees his wife again, though her brother Kahedin remains his close companion.

He becomes a Knight of the Round Table (taking Morholt's old seat) and embarks on the Quest for the Holy Grail before abandoning the idea to stay with Iseult at Lancelot's castle.

Before any modern editions of the Prose Tristan were attempted, scholars were dependent on an extended summary and analysis of all the manuscripts by Eilert Löseth in 1890 (republished in 1974).