In photography, bokeh (/ˈboʊkə/ BOH-kə or /ˈboʊkeɪ/ BOH-kay; Japanese: [boke]) is the aesthetic quality of the blur produced in out-of-focus parts of an image, whether foreground or background or both. It is created by using a wide aperture lens.

Some photographers incorrectly restrict use of the term bokeh to the appearance of bright spots in the out-of-focus area caused by circles of confusion. Bokeh has also been defined as "the way the lens renders out-of-focus points of light". Differences in lens aberrations and aperture shape cause very different bokeh effects. Some lens designs blur the image in a way that is pleasing to the eye, while others produce distracting or unpleasant blurring ("good" and "bad" bokeh, respectively). Photographers may deliberately use a shallow focus technique to create images with prominent out-of-focus regions, accentuating their lens's bokeh.

Bokeh is often most visible around small background highlights, such as specular reflections and light sources, which is why it is often associated with such areas. However, bokeh is not limited to highlights; blur occurs in all regions of an image which are outside the depth of field.

The opposite of bokeh—an image in which multiple distances are visible and all are in focus—is deep focus.

The term comes from the Japanese word boke (暈け/ボケ), which means "blur" or "haze", resulting in boke-aji (ボケ味), the "blur quality". This is derived as a noun form of the verb bokeru, which is written in several ways, with additional meanings and nuances: 暈ける refers to being blurry, hazy or out-of-focus, whereas the 惚ける and 呆ける spellings refer to being mentally hazy, befuddled, childish, senile, or playing stupid. Jisaboke (時差ボケ) (literally, "time difference fog") is the term for jet lag. Nebokeru (寝ぼける) is a verb denoting the actions or condition of someone who is half-asleep, or nodding off. Tobokeru means playing dumb, and toboketa kao refers to a poker face. The related term bokashi (暈かし) means intentional blurring or gradation; that is a noun form of the transitive verb bokasu (暈す), which means to make something blurry, rather than to be blurry.

The English spelling bokeh was popularized in 1997 in Photo Techniques magazine, when Mike Johnston, the editor at the time, commissioned three papers on the topic for the May/June 1997 issue; he altered the spelling to suggest the correct pronunciation to English speakers, saying "it is properly pronounced with bo as in bone and ke as in Kenneth, with equal stress on either syllable".

The spellings bokeh and boke have both been in use since at least 1996, when Merklinger had suggested "or Bokeh if you prefer." The term bokeh has appeared in photography books as early as 1998. It is sometimes pronounced /ˈboʊkə/ BOH-kə.

Though difficult to quantify, some lenses have subjectively more pleasing out-of-focus areas. "Good" bokeh is especially important for macro lenses and long telephoto lenses, because they are typically used in situations that produce shallow depth of field. Good bokeh is also important for medium telephoto lenses (typically 85–150 mm on 35 mm format). When used in portrait photography (for their "natural" perspective), the photographer usually wants a shallow depth of field, so that the subject stands out sharply against a blurred background.^{[citation needed]}