Born in France of Sicilian parents, Roberto Alagna studied music in Paris. He gained notoriety by winning first prize in the 1988 Luciano Pavarotti Competition and soon made his stage debut as Alfredo in La Traviata with the Glyndebourne Touring Opera Company, soon to be followed by debuts in Montpellier, Monte Carlo, and the Teatro alla Scala in Milan (also in La Traviata). His Teatro alla Scala debut came at the invitation of Riccardo Muti in a fabled production with Tiziana Fabbricini which was telecast. In 1990 he sang Rodolfo in Puccini's La Bohème — a role that has become one of his most popular; it was also the role of his Covent Garden Opera debut in 1992 and his Metropolitan Opera debut in 1996. Another role which was very important during the early part of his career was the title role in Gounod's Romeo et Juliette, which he has sung with great success in Paris, London, and New York.
This role proved to be even more important for his personal life, as he met his second wife, Angela Gheorghiu, while they were performing this opera together. His first wife had died after a lengthy illness, and this new romance brought a renewed warmth and passion to his performances. Their performances of L'elisir d'amore, La Bohème, and Werther are greatly admired, and together the two became one of opera's few genuine double attractions, but separated for a period beginning in 2009 and eventually divorced in 2013. He then began a relationship with soprano Aleksandra Kurzak, marrying her in 2015, and again becoming part of a coupled attaction on stage and recordings.
Alagna is known to introduce acrobatic tricks into productions of L'elisir d'amore which few other tenors would attempt. His appearances in 1996 at the Theatre-Chatelet Paris and Covent Garden Opera, London, as Don Carlo in the original French version of Verdi's opera has helped bring the French edition back to the fore. Other operas which have proved successful for Alagna are Rigoletto, Macbeth, Lucia di Lammermoor, Roberto Devereux, L'amico Fritz, Carmen, and La Rondine.
Alagna is a self-taught tenor who learned his craft by listening to recordings to pick up ideas and find those that work for him. He usually mentions two of his predecessors when asked whose recordings were most influential; these are Beniamino Gigli and Nicolai Gedda. He feels his voice is like Gedda's in its brightness and timber. His recordings of La Bohème on Decca and Romeo et Juliette on EMI display some attempts at the vocal refinements which characterized Gedda's singing. Alagna's willingness to step beyond the standard score is displayed in the use of an alternative version of "Una furtiva lágrima" in his London recording of L'elisir d'amore, using the new critical edition of La Bohème in the Decca recording with Chailly, as well as singing the original French version of Don Carlo. His voice is a very fine lyric tenor with a bright and ringing upper register, but when it is put under pressure it tends to turn harsh. With the assumption on stage and on recording of Verdi's Don Carlo and both Werther and Manon of Massenet, Alagna moved into more dramatic roles, and in his recordings of the early 2000s he moved easily around the heart of the operatic repertory.