A dacha (Russian: дача, IPA: [ˈdatɕə] (listen)) is a seasonal or year-round second home, often located in the exurbs of post-Soviet countries, including Russia. A cottage (коттедж, kottedzh) or shack serving as a family's main or only home, or an outbuilding, is not considered a dacha, although some dachas recently have been converted to year-round residences and vice versa.

The noun "dacha", coming from verb "davat" (to give), originally referred to land allotted by the tsar to his nobles; and indeed the dacha in Soviet times is similar to the allotment in some Western countries – a piece of land allotted, normally free, to citizens by the local government for gardening or growing vegetables for personal consumption. With time the name for the land was applied to the building on it. In some cases, owners occupy their dachas for part of the year and rent them to urban residents as summer retreats. People living in dachas are colloquially called dachniki (дачники); the term usually refers not only to dacha dwellers but to a distinctive lifestyle. The Russian term is often said to have no exact counterpart in English.

Dachas are common in Russia, and are also widespread in most parts of the former Soviet Union and in some countries of the former Eastern Bloc. Surveys in 1993–1994 suggest about 25% of Russian families living in large cities had dachas. Most dachas are in colonies of dachas and garden plots near large cities. These clusters have existed since the Soviet era, and consist of numerous small, typically 600-square-metre (0.15-acre), land plots. They were initially intended only as recreation getaways of city dwellers and for growing small gardens for food.

Dachas originated as small country estates given as a gift by the tsar, and have been popular among the Russian upper- and middle-classes ever since. During the Soviet era, many dachas were state-owned, and were given to the people. The government of the Russian Federation continues to own State dachas (gosdacha) used by the president and other officials. They were extremely popular in the Soviet Union.

As regulations severely restricted the size and type of dacha buildings for ordinary people during the Soviet period, permitted features such as large attics or glazed verandas became extremely widespread and often oversized. In the period from the 1960s to 1985 legal limitations were especially strict: only single-story summer houses without permanent heating and with living areas less than 25 m² (269 sq ft) were allowed as second housing (though older dachas that did not meet these requirements continued to exist). In the 1980s planners loosened the rules, and since 1990 all such limitations have been eliminated. As of 2019, about 62% of Russians own dachas.