Chinese characters may have several variant forms—visually distinct glyphs that represent the same underlying meaning and pronunciation. Variants of a given character are allographs of one another, and many are directly analogous to allographs present in the English alphabet, such as the double-storey ⟨a⟩ and single-storey ⟨ɑ⟩ variants of the letter A, with the latter more commonly appearing in handwriting. Some contexts require usage of specific variants.

Before the 20th century, variation in the shape of characters was ubiquitous, a dynamic which continued after the invention of woodblock printing. For example, prior to the Qin dynasty (221–206 BC) the character meaning 'bright' was written as either 明 or 朙—with either 日 'Sun' or 囧 'window' on the left, with the 月 'Moon' component on the right. Li Si (d. 208 BC), the Chancellor of Qin, attempted to universalize the Qin small seal script across China following the wars that had politically unified the country for the first time. Li prescribed the 朙 form of the word for 'bright', but some scribes ignored this and continued to write the character as 明. However, the increased usage of 朙 was followed by proliferation of a third variant: 眀, with 目 'eye' on the left—likely derived as a contraction of 朙. Ultimately, 明 became the character's standard form.

New variants also result from larger shifts in the writing system as a whole, such as the process of libian and liding that resulted in the clerical script. According to the palaeographer Qiu Xigui, the broadest trend in the evolution of Chinese characters over their history has been simplification, both in graphical shape (字形; zìxíng), the "external appearances of individual graphs", and in graphical form (字体; 字體; zìtǐ), "overall changes in the distinguishing features of graphic[al] shape and calligraphic style, [...] in most cases refer[ring] to rather obvious and rather substantial changes". Libian often involved significant omissions, additions, or transmutations of the forms used by Qin small seal script, while liding is the direct regularization and linearization of shapes to convert them into clerical forms while preserving their original structure. For example, the character for 'year' underwent liding to the clerical script form 秊, while the same character after undergoing libian resulted in the orthodox form 年. Similarly, libian and liding created the two distinct characters 虎 and 乕 for 'tiger'.

There are variants that arise through the use of different radicals to refer to specific definitions of a polysemous character. For instance, the character 雕 could mean either 'a type of hawk' or 'carve'. Variants using different radicals to specify thus developed: respectively 鵰, with a ⿃ 'BIRD' radical, and 琱, with a ⽟ 'JADE' radical.

In rare cases, two characters in ancient Chinese with similar meanings were confused and conflated when their modern Chinese readings merged, for example, 飢 and 饑, are both read as jī and mean 'famine', used interchangeably in the modern language, even though 飢 initially meant 'insufficient food to satiate' and 饑 meant 'famine' in Old Chinese. The two characters formerly belonged to two different Old Chinese rime groups (脂 and 微 groups, respectively) which indicates they had different pronunciations back then. A similar situation is responsible for the existence of variants of the particle 於 'in' which had the ancient form 于, now used as its simplified form. In each case above, variants were merged into single simplified forms.

Character forms that are most orthodox are known as orthodox variants (正字; zhèngzì), which is sometimes taken as mean the forms present in the Kangxi Dictionary (康熙字典體; Kāngxī zìdiǎn tǐ), which usually represent the orthodox forms used in late imperial China. Non-orthodox forms are known as folk variants (俗字; súzì; Revised Romanization: sokja; Hepburn: zokuji). Some folk variants are longstanding abbreviations or calligraphic forms, and later became the basis for the simplified forms adopted on the mainland. For example, 痴 is a folk variant corresponding to the orthodox form 癡 'foolish'. These forms differ by their phonetic component, with the folk variant using a character with a "close enough" pronunciation but having much less strokes and thus quicker to write. In mainland China, simplified forms are called xin zixing, typically contrasting with jiu zixing, which are usually the Kangxi form.

Orthodox and vulgar forms may only differ by the length or location of individual strokes, whether certain strokes intersect, or the presence or absence of minor strokes (dots). These are often not considered to amount to being discrete variants. For instance, 述 is the new form of the character with traditional orthography 述 'recount', 'describe'. As another example, the surname 吴, also the name of an ancient state, is the 'new character shape' form of the character traditionally written 吳.

Character variant exist throughout every writing system that uses Chinese characters, including written Chinese, Japanese, and Korean. Several governments of countries that speak these languages have standardized their writing systems by specifying certain variants as the standard form. The choice of which variants to use has resulted in some bifurcation of written Chinese between simplified and traditional forms. The standardization of simplified forms in Japan was distinct from the process in mainland China.