Paraguayan Legion (spanish: Legión Paraguaya) was a military unit led by colonel Juan Francisco Decoud and Fernando Iturburu that was formed in Argentina during the Paraguayan War and consisted mainly of Paraguayan exiles and opponents of Francisco Solano López regime. Due to mistrust between the allied Argentina and Brazil, the Legion never developed into a strong fighting unit, as Brazilians distrusted this unit created by Argentina. They started fighting only in March 1869 but under Paraguayan flag.
Legionnaires dominated the political scene during the Liberal period of the first post-war years. The first Provisional government, the Triumvirate of 1869 included two Legionnaires Jose Diaz de Bedoya and Carlos Loizaga.
Politically legionnaires quickly split into Decoud faction and Bareiro faction. Decoud faction was involved in the formation of Liberal Party in 1887. The former Lopez supporters and nationalists who in 1887 established the Colorado Party, used this to portray Liberals as a product of traitors, despite the fact, that many signers of the Colorado 1887 founding manifesto were former legionnaires as well.