Omegaverse is a subgenre of speculative erotic fiction, and originally a subgenre of erotic slash fan fiction. It is an alternate universe (AU) of speculative erotic fiction that started in the Supernatural fandom. The premise of Omegaverse is that a dominance hierarchy exists in humans, which are divided into dominant "alphas", neutral "betas", and submissive "omegas". The characters in Omegaverse are often werewolves, but sometimes they are just humans with special features. The genre often features other fantasy elements, such as the presence of werewolves or other fantastical creatures.

One of the defining characteristics of Omegaverse is the use of (debunked) wolf social dynamics such as alphas and betas, which is not the same thing as the whole alpha beta sigma that some people believe is reality for humans. Mpreg (male pregnancy) is also extremely common in Omegaverse, largely because the entire concept started in gay supernatural fanfic and the fans wanted destiel to have babies.

Omegaverse has become both extremely popular and controversial in fandom circles. Some condemn it as revolting and sick, affirming that it reinforces patriarchal values and a rape culture, objecting to its roots in bestiality fiction and the power imbalances between genders. Conversely, others appreciate how it deconstructs bodies and gender roles, offering subversive social commentary on queer identity and oppression.

Despite not using the term "omega", the story created many of the characteristics later associated with the Omegaverse genre. The Omegaverse exploded in popularity in 2017, quickly becoming a frequent subject of fan fiction writers. As of July 2018, over 39,000 Omegaverse fan works had been published on the fan fiction website Archive of Our Own, and over 70,000 as of 2020. In addition to these derivative works, Omegaverse has emerged as its own genre of original commercial erotic fiction: roughly 200 Omegaverse novels.