Carlos Diego Mesa Gisbert (born August 12, 1953) is a Bolivian politician, historian and President of Bolivia from October 17, 2003 until his resignation on June 6, 2005.

Mesa was a popular television journalist and personality, known by many for his rectitude and impartiality but loathed by many others for alleged political opportunism. His widespread name recognition prompted the MNR candidate Gonzalo Sánchez de Lozada to pick him as his running mate in the 2002 Bolivian presidential elections. The winning ticket of Sánchez-Mesa took possession on August 6, 2002. As Vice-President, the apolitical Mesa was quickly caught between the proverbial rock and hard place, as a wave of protests and strikes shut down Bolivia in a bitter dispute known as the Bolivian Gas War. The demonstrations eventually forced Sánchez de Lozada to resign and flee the country, leaving Mesa as President of the Republic.

In the short year and a half since assuming office, Mesa found himself also under extreme internal and external political pressures over the use of Bolivia's 1.5 trillion cubic meters of natural gas reserves, estimated to be worth billions of dollars (USD).