The queen's men are members of Stannis Baratheon's court that have converted to the faith of R'hllor.
Historically, Queen Selyse Florent was among the first in Dragonstone to convert, and it was initially by her insistence that Stannis took notice of the red priestess, Melisandre. Calling them the "queen's" men alludes to the fact that Selyse is a vocal supporter of Melisandre and of her god, arguably more so than Stannis himself, and helps in telling them apart from the so-called king's men who are also supporters of Stannis's cause yet have kept the Faith of the Seven. However, an alternate interpretation is that the queen they are loyal to is not Selyse but rather Melisandre, who is in many senses closer to Stannis than Selyse.
They often have a fiery heart, the emblem of the Lord of Light, embroidered on their breasts signifying their allegiance.
One realm, one god, one king! STANNIS! STANNIS! ONE REALM, ONE GOD, ONE KING!
They would as gladly burn me as those logs and broken branches.
—Asha Greyjoy's thoughts
Known Queen's Men
Game of Thrones is roughly based on the storylines of A Song of Ice and Fire, set in the fictional Seven Kingdoms of Westeros and the continent of Essos. The series chronicles the violent dynastic struggles among the realm's noble families for the Iron Throne, while other families fight for independence from it. It opens with additional threats in the icy North and Essos in the east. Dive deep in the big world of Westeros or Essos.With us, you will learn all the history and geography about all houses castles and much more.