The Workers' Vanguard Party (Spanish: Vanguardia Obrera, VO) was a small Trotskyist political party in Bolivia. The Workers' Vanguard Party was established by a dissident fraction which broke away from the Communist Vanguard of the Revolutionary Workers' Party in 1978.It was led by and . The VO took part in elections in 1978 and presented as its presidential candidate Ricardo Catoira Marín and Filemón Escobar as vice-presidential candidate. In 1980 the VO took part in an electoral coalition Democratic and Popular Union backing Hernán Siles Zuazo.