Montserrat Caballé rose to prominence through an extraordinary stroke of fortune that ultimately established her as one of Spain's foremost sopranos, sharing equal renown only with her fellow Barcelonian Victoria de los Angeles. Born Maria de Montserrat Viviana Concepción Caballé i Folch and named for the celebrated Catalan monastery of Montserrat, she entered the world under circumstances that prompted her parents to pledge this distinctive title should she survive infancy. Her early vocal training occurred at a convent school before she enrolled at the age of eight in Barcelona's Conservatorio del Liceo, where her principal instructors included Eugenia Kenny, Conchita Badea, and Napoleone Annovazzi. Upon completing her studies in 1954 she received the Liceo's Gold Medal.
Her professional entrance took place in Madrid with a performance in the oratorio El pesebre by the eminent Catalan cellist Pau (Pablo) Casals. Subsequent engagements in Italy brought only modest parts at various theaters until 1956, when she affiliated with the Basel Opera. While advancing through secondary assignments there, she assumed the role of Mimì in Puccini's La Bohème after an indisposed colleague withdrew, and the resulting acclaim propelled her into leading parts such as Pamina in The Magic Flute, Tosca, Aïda, Marta in Tiefland, and the Richard Strauss heroines Arabella, Chrysothemis in Elektra, and Salome. Appearances across Europe in Bremen, Milan, Vienna, Barcelona, and Lisbon further solidified her standing as she portrayed Violetta in La Traviata, Tatiana in Yevgeny Onegin, Armida and Rusalka by Dvořák, and Marie in Wozzeck. Her La Scala debut arrived in 1960 as a Flower Maiden in Parsifal, and she performed Massenet's Manon in Mexico City in 1964.
On April 20, 1965, she stepped in at the last moment for the ailing Marilyn Horne in a concert presentation of Donizetti's Lucrezia Borgia, earning an overwhelming ovation that conferred "overnight" superstardom. She soon became central to the renewed appreciation of bel canto works by Bellini and Donizetti, many of them mounted expressly for her, with her portrayals of Elizabeth I in Roberto Devereux and Mary Queen of Scots in Maria Stuarda attaining legendary status. A 1971 concert reading of Maria Stuarda marked the London debut of her fellow Barcelonian José Carreras, after which she actively supported his rising trajectory. She first appeared at the Metropolitan Opera in 1965 as Marguerite in Faust. Although her primary focus remained on Verdi's major dramatic roles, her repertoire also encompassed the Marschallin in Der Rosenkavalier, the Countess in The Marriage of Figaro, and Queen Isabella in the 1989 Barcelona premiere of Leonardo Balada's Cristóbal Colón.
Uncommon crossover appeal marked her later activities. She contributed to two tracks on an album by new age composer Vangelis and formed a notable partnership with Freddie Mercury of the rock group Queen, for whom she inspired the composition Exercises in Free Love. Their collaboration appeared on the hit album Barcelona, whose title track and parent recording both achieved strong pop-chart placements. In 1964 she wed Spanish tenor Bernabé Martí; the couple had two children, Bernabé Martí, Jr. and Montserrat Martí, the latter of whom established her own career as a soprano. Caballé co-established the Concurs Internacional de Cant Montserrat Caballé, an annual vocal competition in the Principality of Andorra, in 1997 and led master classes connected to the event. Her final performance occurred in 2014, and she passed away on October 6, 2018, shortly after hospital admission.