Cisnormativity or cissexual assumption is the assumption that everyone is, or ought to be, cisgender. The term can further refer to a wider range of presumptions about gender assignment, such as the presumption of a gender binary, or expectations of conformity to gender roles even when transgender identities are otherwise acknowledged. Cisnormativity is a form of cisgenderism, an ideology which promotes various normative ideas about gender, to the invalidation of individuals' own gender identities, analogous to heterosexism or ableism.

Cisnormativity is widespread in many areas of society. In speech, cisnormativity manifests as a separation of cisgender and transgender people where cisgender individuals are considered normal and transgender people, an exception. In institutions, cisnormativity may be seen in the ways gender transition is legally regulated, and in the binary division of legal gender in most jurisdictions; schools often enforce a strict division between genders, which leads to the stigmatization of transgender people. Cisnormativity also motivates bullying and harassment in educational settings. In health care, cisnormative attitudes and systems have diverse negative effects on transgender patients, including pathologization, erasure, and distrust towards healthcare practicioners.

Cisnormativity is closely tied to heteronormativity. The combination of the two, termed hetero-cis-normativity or cisheteronormativity, represents the societally dominant view that sex, gender, and sexual orientation are all congruent.

The term cisnormativity was coined in a 2009 article published in the Journal of the Association of Nurses in AIDS Care (JANAC), which defines cisnormativity as "the expectation that all people are cissexual". The SAGE Encyclopedia of Trans Studies states that cisnormativity is "the presumption that most people do, or should, conform to the norms about gender assignment in their society". It elaborates: "'cisnormative' behavior varies depending on the gender norms in place within a given society. For example, in some societies, having only 'woman' and 'man' as gender categories would not be cisnormative".

In 2007, transfeminist author Julia Serano wrote in Whipping Girl that "[cissexual assumption] occurs when a cissexual makes the common, albeit mistaken, assumption that the way they experience their physical and subconscious sexes [...] applies to everyone else in the world". She argues that cisgender people "indiscriminately project" their experience of gender identity onto all others, "transforming cissexuality into a human attribute that is taken for granted".

A related concept is that of cisgenderism (also known as cissexism), defined by Erica Lennon and Brian J. Millster writing for Transgender Studies Quarterly as "the cultural and systemic ideology that denies, denigrates, or pathologizes self-identified gender identities that do not align with assigned gender at birth as well as resulting behavior, expression, and community". Cisgenderism was proposed as an alternative concept to transphobia, with the intention of drawing focus to a systemic ideology, rather than an individual "phobia". This draws from the earlier distinction between heterosexism and homophobia. According to The SAGE Encyclopedia, cisnormativity is one form of cisgenderism.

Academic literature identifies cisnormativity as intersectional with endosexism, sexism, heterosexism, bisexual erasure, classism, racism, ageism, and nationalism. Cisnormativity contributes to patriarchy by providing a rigid division of people into genders and gender roles.

Cisnormativity often appears together with heteronormativity. According to Judith Butler, the dominant view of gender assumes a "causal continuity among sex, gender, and desire". In 2012, sociologist Meredith Worthen coined the term hetero-cis-normativity for this phenomenon: