Ink wash painting (simplified Chinese: 水墨画; traditional Chinese: 水墨畫; pinyin: shuǐmòhuà) is a type of Chinese ink brush painting which uses washes of black ink, such as that used in East Asian calligraphy, in different concentrations. It emerged during the Tang dynasty of China (618–907), and overturned earlier, more realistic techniques. It is typically monochrome, using only shades of black, with a great emphasis on virtuoso brushwork and conveying the perceived "spirit" or "essence" of a subject over direct imitation. Ink wash painting flourished from the Song dynasty in China (960–1279) onwards, as well as in Japan after it was introduced by Zen Buddhist monks in the 14th century. Some Western scholars divide Chinese painting (including ink wash painting) into three periods: times of representation, times of expression, and historical Oriental art. Chinese scholars have their own views which may be different; they believe that contemporary Chinese ink wash paintings are the pluralistic continuation of multiple historical traditions.

In China, Japan and, to a lesser extent, Korea, ink wash painting formed a distinct stylistic tradition with a different set of artists working in it than from those in other types of painting. In China especially it was a gentlemanly occupation associated with poetry and calligraphy. It was often produced by the scholar-official or literati class, ideally illustrating their own poetry and producing the paintings as gifts for friends or patrons, rather than painting for payment. In practice a talented painter often had an advantage in climbing the bureaucratic ladder. In Korea, painters were less segregated, and more willing to paint in two techniques, such as mixing areas of colour with monochrome ink, for example in painting the faces of figures.

The vertical hanging scroll was the classic format; the long horizontal handscroll format tended to be associated with professional coloured painting, but was also used for literati painting. In both formats paintings were generally kept rolled up, and brought out for the owner to admire, often with a small group of friends. Chinese collectors liked to stamp paintings with their seals and usually in red inkpad; sometimes they would add poems or notes of appreciation. Some old and famous paintings have become very disfigured by this; the Qianlong Emperor was a particular offender.

In landscape painting the scenes depicted are typically imaginary or very loose adaptations of actual views. The shan shui style of mountain landscapes are by far the most common, often evoking particular areas traditionally famous for their beauty, from which the artist may have been very distant.

East Asian writing on aesthetics is generally consistent in saying that the goal of ink and wash painting is not simply to reproduce the appearance of the subject, but to capture its spirit. To paint a horse the ink-wash painting artist must understand its temperament better than its muscles and bones. To paint a flower there is no need to perfectly match its petals and colors, but it is essential to convey its liveliness and fragrance. It has been compared to the later Western movement of Impressionism. It is also particularly associated with the Chán or Zen sect of Buddhism, which emphasizes "simplicity, spontaneity and self-expression", and Daoism, which emphasizes "spontaneity and harmony with nature," especially when compared with the less spiritually-oriented Confucianism.

East Asian ink wash painting has long inspired modern artists in the West. In his classic book Composition, American artist and educator Arthur Wesley Dow (1857–1922) wrote this about ink wash painting: "The painter... put upon the paper the fewest possible lines and tones; just enough to cause form, texture and effect to be felt. Every brush-touch must be full-charged with meaning, and useless detail eliminated. Put together all the good points in such a method, and you have the qualities of the highest art". Dow's fascination with ink wash painting not only shaped his own approach to art but also helped free many American modernists of the era, including his student Georgia O'Keeffe, from what he called a "story-telling" approach. Dow strived for harmonic compositions through three elements: line, shading, and color. He advocated practicing with East Asian brushes and ink to develop aesthetic acuity with line and shading.

Ink wash painting uses tonality and shading achieved by varying the ink density, both by differential grinding of the ink stick in water and by varying the ink load and pressure within a single brushstroke. Ink wash painting artists spend years practicing basic brush strokes to refine their brush movement and ink flow. These skills are closely related to those needed for basic writing in East Asian characters, and then for calligraphy, which essentially use the same ink and brushes. In the hand of a master, a single stroke can produce considerable variations in tonality, from deep black to silvery gray. Thus, in its original context, shading means more than just dark-light arrangement: It is the basis for the nuance in tonality found in East Asian ink wash painting and brush-and-ink calligraphy.

Once a stroke is painted it cannot be changed or erased. As a result, ink and wash painting is a technically demanding art form requiring great skill, concentration, and years of training.