Guillermo Lora is a Trotskyist leader in Bolivia. Lora has been active in the Revolutionary Workers Party (Bolivia) (POR) since the early 1940s and is its best known leader. He has led it through a number of crisis including the revolutionary crisis of 1952 when the small POR was very close to the leadership of the miners union and the trade union central.

Since then the POR has had a number of splits and has remained a small group. However, Lora's POR is the largest Trotskyist group in the country. In the split of the Fourth International that took place in 1953, Lora played no role but was sympathetic to the International Committee of the Fourth International later. It sought to join the ICFI in the 1960s but this was at a time when the ICFI was riven by factional divisions between Pierre Lambert and Gerry Healy. Lora took the part of Lambert before leaving some time later with the Fourth Internationalist tendency based on his party and the Workers party in Argentina. The two groups split some time later and the POR remains more or less isolated at the international level.

Lora was also the central leader of the POR during the revolutionary events of the early 1970s. While opposing the focoist guerilla campaign of Che Guevara, they did solidarise with him in the 1960s.