Gruit is a generic term referring to the herb mixtures used to flavor and preserve beer before the general use of hops took hold in the 15th and 16th centuries in Europe. Gruit was most commonly composed of sweet gale (also known as bog myrtle; see bog myrtle), yarrow, and wild (or marsh) rosemary, but could also include other botanicals such as heather, juniper, ginger, caraway, and cinnamon. Hops were also sometimes a part of the mixture. In Britain a distinction was drawn between “ale” flavored with gruit mixtures and “beer” brewed with hops.

Though a taste for hopped beers did arise among brewers and drinkers beginning in about the 11th century, the demise of gruit had less to do with preferential supersession by hops than political, religious, and moral struggles within the individual countries in which it was used. With the Catholic Church having widely held a monopoly on the sale and taxation of gruit, the use of hops in brewing beer was nothing short of a revolutionary act as German princes asserted their independence just as the Reformation dawned. The Bavarian Purity Law (Reinheitsgebot) of 1516 in fact roughly coincided with the earliest public acts of Martin Luther. See reinheitsgebot. Additionally, puritanical interdictions against the use in beer of substances putatively psychotropic and aphrodisiacal as well as the condemnation of the practices of brewsters as tantamount to witchcraft helped hasten the general discontinuation of the production and use of gruit.

Some modern examples of gruit ales do exist, notably Fraoch and Alba by the Scottish brewers Williams Brothers and The Wind Cries Mari by Cambridge Brewing Co. of Cambridge, Massachusetts.