Chữ Nôm (𡨸喃, IPA: [t͡ɕɯ˦ˀ˥ nom˧˧]) is a logographic writing system formerly used to write the Vietnamese language. It uses Chinese characters to represent Sino-Vietnamese vocabulary and some native Vietnamese words, with other words represented by new characters created using a variety of methods, including phono-semantic compounds. This composite script was therefore highly complex and was accessible to the less than five percent of the Vietnamese population who had mastered written Chinese.

Although all formal writing in Vietnam was done in Classical Chinese until the early 20th century (except for two brief interludes), between the 15th and 19th centuries some Vietnamese literati used chữ Nôm to create popular works in the vernacular, many in verse. One of the best-known pieces of Vietnamese literature, The Tale of Kiều, was written in chữ Nôm by Nguyễn Du.

The Vietnamese alphabet created by Portuguese Jesuit missionaries, with the earliest known usage occurring in the 17th century, replaced chữ Nôm as the preferred way to record Vietnamese literature from the 1920s. While Chinese characters are still used for decorative, historic and ceremonial value, chữ Nôm has fallen out of mainstream use in modern Vietnam. In the 21st century, chữ Nôm is being used in Vietnam for historical and liturgical purposes. The Institute of Hán-Nôm Studies at Hanoi is the main research centre for pre-modern texts from Vietnam, both Chinese-language texts written in Chinese characters (chữ Hán) and Vietnamese-language texts in chữ Nôm.

The Vietnamese word chữ 'character' is derived from the Middle Chinese word dzi^H 字, meaning '[Chinese] character'. The word Nôm 'Southern' is derived from the Middle Chinese word nom 南, meaning 'south'. It could also be based on the dialectal pronunciation from the South Central dialects (most notably in the name of province of Quảng Nam, known locally as Quảng Nôm).

There are many ways to write the name chữ Nôm in chữ Nôm characters. The word chữ may be written as 字, 𫳘(⿰字宁), 𡨸, 𫿰(⿰字文), 𡦂(⿰字字), 𲂯(⿰貝字), 𱚂(⿱字渚), or 宁, while Nôm is written as 喃.

Chữ Nôm is the logographic writing system of the Vietnamese language. It is based on the Chinese writing system but adds a large number of new characters to make it fit the Vietnamese language. Common historical terms for chữ Nôm were Quốc Âm (國音, 'national sound') and Quốc ngữ (國語, 'national language').

In Vietnamese, Chinese characters are called chữ Hán (𡨸漢 'Han characters'), chữ Nho (𡨸儒 'Confucian characters', due to the connection with Confucianism) and uncommonly as Hán tự (漢字 'Han characters'). Hán văn (漢文) refers literature written in Literary Chinese.

The term Hán Nôm (漢喃 'Han and chữ Nôm characters') in Vietnamese designates the whole body of premodern written materials from Vietnam, either written in Chinese (chữ Hán) or in Vietnamese (chữ Nôm). Hán and Nôm could also be found in the same document side by side, for example, in the case of translations of books on Chinese medicine. The Buddhist history Cổ Châu Pháp Vân phật bản hạnh ngữ lục (1752) gives the story of early Buddhism in Vietnam both in Hán script and in a parallel Nôm translation. The Jesuit Girolamo Maiorica (1605–1656) had also used parallel Hán and Nôm texts.