We know of several alchemists through the alchemical manuscripts and books that are mentioned or found throughout the books and game. There may be more, who spent less time writing, and more time simply experimenting, who have left no trace in "history". Some alchemists from the books and game are listed below.
In The Witcher, most alchemists are also merchants and at least one is a witch. In fact, the only known alchemist in the game who is not also a merchant is Azar Javed.