The Uruguayan Civil War, also known as Guerra Grande, was a series of armed conflicts that took place between the Colorado Party and the National Party in Uruguay from 1839 to 1851. The two parties received backing from foreign sources including both neighbouring countries such as the Empire of Brazil and the Argentine Confederation as well as imperial powers, primarily the British Empire and the Kingdom of France, but also a legion of Italian volunteers including Giuseppe Garibaldi. The nine-year siege of Montevideo captured the imagination of European writers such as Alexandre Dumas.

The political scene in Uruguay during the 1830s became split between two parties, the conservative Blancos ("Whites") and the liberal Colorados (literally "coloureds", more usually "Reds"). The Colorados were led by Fructuoso Rivera and represented the business interests of Montevideo; the Blancos were headed by Manuel Oribe, who looked after the agricultural interests of the countryside and promoted protectionism. The two groups took their names from the color of the armbands that they wore; initially, the Colorados wore blue, but when it faded in the sun, they replaced it with red.

A civil war is a war between organized groups within the same nation state or republic, or, less commonly, between two countries created from a formerly united nation state. The aim of one side may be to take control of the country or a region, to achieve independence for a region, or to change government policies. The term is a calque of the Latin bellum civile which was used to refer to the various civil wars of the Roman Republic in the 1st century BC.

A civil war is a high-intensity conflict, often involving regular armed forces, that is sustained, organized and large-scale. Civil wars may result in large numbers of casualties and the consumption of significant resources.

Civil wars since the end of World War II have lasted on average just over four years, a dramatic rise from the one-and-a-half year average of the 1900-1944 period. While the rate of emergence of new civil wars has been relatively steady since the mid-19th century, the increasing length of those wars resulted in increasing numbers of wars ongoing at any one time. For example, there were no more than five civil wars underway simultaneously in the first half of the 20th century, while over 20 concurrent civil wars were occurring at the end of the Cold War, before a significant decrease as conflicts strongly associated with the superpower rivalry came to an end. Since 1945, civil wars have resulted in the deaths of over 25 million people, as well as the forced displacement of millions more. Civil wars have further resulted in economic collapse; Burma (Myanmar), Uganda and Angola are examples of nations that were considered to have promising futures before being engulfed in civil wars.