Born on 8 April 1827 to a wealthy landowner, Betances received his medical degree from the University of Paris in 1855. Upon his return to Mayagüez, he founded a hospital and worked to save Puerto Ricans from the ravages of a cholera epidemic. That year he and others founded a clandestine society dedicated to the liberation of the slaves. The Spanish colonial government exiled him for these activities several times. In 1867, he fled to the present-day Dominican Republic where he founded the Revolutionary Committee of Puerto Rico. The following year he organized an armed expedition that led to the abortive insurrection of September 23, known as the Grito de Lares.
He returned to France where he served as delegate to the Cuban Revolutionary Junta, Secretary of the Dominican Legation, and founded the Society of Latin American Union. Although he spent his remaining years away from his homeland, he viewed the abolition of slavery there on March 22, 1873 with great satisfaction. For his contributions to literature, the French government awarded him its Legion of Honor. Betances died on 16 September 1898. His remains returned to Puerto Rico in 1920 where they were buried in his birthplace.