The Sorcerer's Guild (Japanese: 魔道士まどうし協会きょうかい Kanji translation: Sorcerer Association, Romaji: madōshi kyōkai) is an organization consisting of practitioners of magic in the area surrounded by the mazoku barrier of the Slayers world.

The Sorcerer's Guild is known to be founded hundreds of years earlier before Lina Inverse was born, although the exact date is yet to be revealed. It currently exists as several mostly independent associations in major cities. These local branches were originally under the authority of the guild headquarters in Sairaag, but after the city was destroyed for the first time by Zanaffar, this centralized government ceased to exist, and was not reestablished since.

Even Lina Inverse assumed the role of a guild instructor a few times

The guild holds possession of a considerable portion of the magic lore available, although more exotic texts such as Clair Bible manuscripts seem to be missing from their libraries. Aside of being the primary source of arcane knowledge, the guild is also responsible for the education of would-be sorcerers. (It is unknown whether or not shrine maidens are also taught by the guild.) Students at the Sorcerer's Guild are acquainted with the fundamentals of magic theory and spellcasting, but when it comes to spells, only simple and usually non-destructive incantations are made available to them, mostly from the white and shamanistic category, and not even all of those. Unlock and Sleeping are notorious examples of spells that the guild attempts to hold back, as their simplicity and effects make them easy to abuse. If the pupil wants to know more powerful magic, he usually needs to invent the spell himself or use the guild library, which cannot be considered cheap by any means. The Sorcerer's Guild protects its favored position in magical education and knowledge by forbidding sorcerers to teach arcane fundamentals or spells to a third party without permission, although this restriction is hard to enforce and is not upheld by all.

A person who studied at the guild is not considered a sorcerer yet. In order to gain that title, one must prove him/herself in a special test, of which not much is known currently, aside of the fact that the ability to cast Fireball seems to be a requirement. If the candidate passes, he/she is given a color title (Lina the Pink, for instance) and a matching robe which identifies him/her as a member of the spellcasting community.

When passing through larger settlements, Lina Inverse often pays a visit to the local Sorcerer's Guild, hoping to stumble upon some knowledge or rumor she could find useful. Aside of requiring financial compensation, the guild occasionally asks her to fill in as an instructor for a short time.