The word cisgender (often shortened to cis; sometimes cissexual) describes a person whose gender identity corresponds to their sex assigned at birth, i.e., someone who is not transgender. The prefix cis- is Latin and means on this side of. The term cisgender was coined in 1994 as an antonym to transgender, and entered into dictionaries starting in 2015 as a result of changes in social discourse about gender.

Related concepts are cisnormativity (the presumption that cisgender identity is preferred or normal) and cissexism (bias or prejudice favoring cisgender people).

The term cisgender has its origin in the Latin-derived prefix cis-, meaning 'on this side of', which is the opposite of trans-, meaning 'across from' or 'on the other side of'. This usage can be seen in the cis–trans distinction in chemistry, the cis and trans sides of the Golgi apparatus in cellular biology, the ancient Roman term Cisalpine Gaul (i.e. 'Gaul on this side of the Alps'), and Cisjordan (as distinguished from Transjordan). In cisgender, cis- describes the alignment of gender identity with assigned sex.

Marquis Bey states that "proto-cisgender discourse" arose in German in 1914, when Ernst Burchard introduced the cis/trans distinction to sexology by contrasting "cisvestitismus, or a type of inclination to wear gender-conforming clothing, [...] with transvestitismus, or cross-dressing." German sexologist Volkmar Sigusch used the term cissexual (zissexuell in German) in his two-part 1991 article "Die Transsexuellen und unser nosomorpher Blick" ("Transsexuals and our nosomorphic view"); in 1998, he said he had coined the term there.

The term cisgender was coined in English in 1994 in a Usenet newsgroup about transgender topics as Dana Defosse, then a graduate student, sought a way to refer to non-transgender people that avoided marginalizing transgender people or implying that transgender people were an other. John Hollister used it that same year. In 1995, Carl Buijs used it, apparently coining it independently.

Medical academics use the term and have recognized its importance in transgender studies since the 1990s. After the terms cisgender and cissexual were used in a 2006 article in the Journal of Lesbian Studies and Serano's 2007 book Whipping Girl, the former gained further popularity among English-speaking activists and scholars. Cisgender was added to the Oxford English Dictionary in 2015, defined as "designating a person whose sense of personal identity corresponds to the sex and gender assigned to him or her at birth (in contrast with transgender)". Perspectives on History states that since this inclusion, the term has increasingly become common usage.

In the late 1990s, cisgender was popularized on USENET by Laura Blake, who used it prolifically when debating with other users and emphasized the term's linguistic grounding in social constructionism. Blake's concept of a "cisgender ideal" as foundational to transphobia was influential for other transgender Internet users.

In February 2014, Facebook began offering "custom" gender options, allowing users to identify with one or more gender-related terms from a selected list, including cis, cisgender, and others.