An embargo is the partial or complete prohibition of commerce and trade with a particular country, in order to isolate it. Embargos are considered strong diplomatic measures imposed in an effort, by the embargo-imposing-country, to elicit a given national-interest result from the country on which it is imposed. Embargos are similar to economic sanctions and are generally considered legal barriers to trade, not to be confused with blockades, which are often considered to be acts of war.
The Embargo of 1807 was a series of laws passed by the U.S. Congress 1806-1808, during the second term of President Thomas Jefferson. Britain and France were engaged in a major war; the U.S. wanted to remain neutral and trade with both sides, but neither side wanted the other to have the American supplies. The American national-interest goal was to use the new laws to avoid war, punish Britain, and force that country to respect American rights..

One of the most comprehensive attempts at an embargo happened during the Napoleonic Wars. In an attempt to cripple the United Kingdom economically, the Continental System- which forbade European nations from trading with the UK- was created. In practice it was not completely enforceable and was as harmful if not more so to the nations involved than to the British.

The United States imposed an embargo on Cuba's Castro government on February 7, 1962. Misnomered by Cuba as "el bloqueo" (the blockade), it remains as one of the longest standing embargos. While talking some steps to allow limited economic exchanges with Cuba, President Barack Obama stated that, without improved human rights and freedoms by Cuba's current government, the embargo remains "in the national interest of the United States." The embargo has, thus far, had very limited success in bringing about any such changes in Cuban policies, as it is widely criticized and has, more significantly, been completely disregarded, even by many countries considered to be avowed allies of the United States.

Oddly enough, United States law prohibits participation in secondary embargoes. This occurs when one country pressures a business to stop doing business with a third country over issues with which the business is not directly involved. Not only is an American business required not to participate in a secondary embargo, but is also required to report all attempts to get a business to participate in a secondary embargo. The situation which led to these laws are attempts by Arab countries to prevent American companies from doing business with Israel and Iraq.

In effort to punish South Africa for its policies of apartheid, The United Nation General Assembly adopted a voluntary international oil embargo against South Africa on November 20, 1987; that embargo had the support of 130 countries.

Embargoes are complex in their international meaning. In response to embargos, an independent economy or autarky often develops in an area subjected to heavy embargo. Effectiveness of embargos are thus necessarily in direct proportion to the extent and degree of international participation.