Community-supported agriculture (CSA model) or cropsharing is a system that connects producers and consumers within the food system more closely by allowing the consumer to subscribe to the harvest of a certain farm or group of farms. It is an alternative socioeconomic model of agriculture and food distribution that allows the producer and consumer to share the risks of farming. The model is a subcategory of civic agriculture that has an overarching goal of strengthening a sense of community through local markets.

Community-supported agriculture can be considered as a practice of commoning. It is an example of community-led management of the production and distribution of goods and services. The organization of food provisioning through commoning is complementary to the horizontal axis of market mediated food provisioning and the verticality of the state distribution and regulation on food. As a model in which market agents do not interact solely as competitors but as "members of a community collaborating in pursuing a collective action for the commonwealth", it is also recognized and supported by public policies in some countries. Such frameworks of collaboration between public administration and the cooperative sector are known as public-common partnerships (PCP), and have also been established in relation to food. As a prefigurative practice that decommodifies food and “strengthens the imaginary of community as a source of reward and space of emancipation“ CSA has been acknowledged as an important step-stone in a sustainability transition in agri-food systems.

In return for subscribing to a harvest, subscribers receive either a weekly or bi-weekly box of produce or other farm goods. This includes in-season fruits, vegetables, and can expand to dried goods, eggs, milk, meat, etc. Typically, farmers try to cultivate a relationship with subscribers by sending weekly letters of what is happening on the farm, inviting them for harvest, or holding an open-farm event. Some CSAs provide for contributions of labor in lieu of a portion of subscription costs.

The term CSA is mostly used in the United States, Canada and the UK, but a variety of similar production and economic sub-systems are in use worldwide and in Austria and Germany as Solidarische Landwirtschaft (lit. 'solidarity agriculture', abbreviated to Solawi).

The term "community-supported agriculture" was coined in the northeastern United States in the 1980s, influenced by European biodynamic agriculture ideas formulated by Rudolf Steiner. Two European farmers, Jan Vander Tuin from Switzerland and Trauger Groh from Germany, brought European biodynamic farming ideas to the United States in the mid-1980s. Vander Tuin had co-founded a community-supported agricultural project named Topinambur located near Zurich, Switzerland. Coinage of the term "community-supported agriculture" stems from Vander Tuin. This influence led to the separate and simultaneous creation of two CSAs in 1986. The CSA Garden at Great Barrington was created in Massachusetts by Jan Vander Tuin, Susan Witt, and Robyn Van En. The Temple-Wilton Community Farm was created in New Hampshire by Anthony Graham, Trauger Groh, and Lincoln Geiger.

The CSA Garden at Great Barrington remained together until 1990 when many members left to form the Mahaiwe Harvest CSA. One of the original founders, Robyn Van En, became incredibly influential in the CSA movement in America and founded CSA North America in 1992. The Temple-Wilton Community Garden was more successful and still operates as a CSA today. It became an important member of the Wilton community and it receives funding from state, federal, and local sources.

A parallel model called Teikei existed in Japan as early as the mid-1960s. Similarly, Dr. Booker T. Whatley, a professor of agriculture in Alabama, advocated for Clientele Membership Clubs as early as the 1960s.

Since the 1980s, community supported farms have been organized throughout North America—mainly in New England, the Northwest, the Pacific coast, the Upper-Midwest and Canada. North America now has at least 13,000 CSA farms of which 12,549 are in the US according to the United States Department of Agriculture in 2007. The rise of CSAs seems to be correlated with the increase in awareness of the environmental movement in the United States, and because food acquisition from local sources can reduce greenhouse gas emissions, CSAs contribute to climate change mitigation. CSAs have even become popular in urban environments such as the New York City Coalition Against Hunger's CSA program that helps serve under-served communities. One of the largest subscription CSAs was Capay Inc. in Capay Valley, California which in 2010 delivered boxes to 13,000 customers a week as well as selling at 15 farmers markets, operating a retail store, and delivering special orders to restaurants.