Alpha/Beta/Omega or Alpha/Omega (occasionally Alpha/Beta) is a kink trope wherein some or all people have defined biological roles based on a hierarchical system, with the terms originating from animal behaviour research. There may be werewolf, knotting, or other animalistic elements involved, or the characters may be otherwise purely human.

Alphas are generally dominant and able to impregnate Omegas. Male Alphas usually have a knot when aroused.

Betas are subordinate to Alphas and may or may not be able to impregnate Omegas; in some fanworks Betas aren't present and the trope is known as Alpha/Omega, in others they take the role and functions of Omegas and Omegas aren't present. Betas are often presented as having "normal" human anatomy with none of the special attributes of Alphas or Omegas.

Omegas are generally lowest on the hierarchy (although in some fanworks Omegas are rare and prized). Male Omegas are self-lubricating and have the ability to become pregnant, sometimes referred to as being bred or mated. Lovers may form pair-bonds with a special connection with telepathic or empathetic qualities. Paired Alphas may be jealous and possessive of their mate, while the Omega may become submissive. Omegas and Alphas may go into heat and need to have sex; this may be the only time Omegas are fertile.