The Headless Queen is a motif used in the play Spring Awakening which is eventually inspiration for Moritz's suicide.
Moritz is at Melchior house and begins repeating a story his grandmother often tells him about a beautiful queen with no head, who was one day conquered by a king with two heads. The king's two heads quarreled all the time, so the chief court magician took off one of the king's heads and gave it to the queen. It suited her admirably, and the two got married. Moritz realizes he's been speaking nonsense, but admits that lately he cannot get the headless queen out of his head. Every time he sees a beautiful girl, he can't help but picture her without her head.
"It's just as if I heard my dead grandmother telling me the story of the “Queen Without a Head.” There was once a wonderfully beautiful Queen, beautiful as the sun, more beautiful than all the maidens in the country. Only, unfortunately, she came into the world without a head. She could not eat, not drink, not kiss. She could only communicate with her courtiers by using her soft little hand. With her dainty feet she stamped declarations of war and orders for executions. Then, one day, she was besieged by a King, who, by chance, had two heads, which, year in and year out, disputed with one another so violently that neither could get a word in edgewise. The Court Conjurer-in-chief took off the smallest of these heads and set it upon the Queen's body. And, behold, it became her extraordinarily well! Therefore, the King and the Queen were married, and the two heads disputed no longer, but kissed each other upon the brow, the cheeks and the mouth, and lived thereafter through long, long years of joy and peace.——Delectable nonsense! Since vacation I can't get the headless Queen out of my mind. When I see a pretty girl, I see her without a head——and then presently, I, myself appear to be the headless Queen.——It is possible that someone may be set over me yet."
Moritz's obsession with the headless queen both foreshadows his own end and underscores the connection between sex and violence that is present throughout the play.