Régis Mengus was first drawn to the piano before discovering singing at the Conservatoire de Metz.

He made his stage debut at the Opéra de Metz and quickly made a name for himself, notably in Carmen at the opera houses of Lille and Caen, Véronique at the Opéra de Saint-Étienne and Faust at the Opéra de Metz.

He broadened his repertoire with leading roles such as Danilo (The Merry Widow) at the Opéra de Reims, the Opéra de Nice and then the Opéra de Lausanne, and Marcello (La bohème) at the Opéra de Reims.

In October 2013 he won first prize and the audience prize at the Vivonne International Singing Competition, followed in March 2014 by first prize, the audience prize and the special prize for low voices at the Bordeaux International Competition, as well as the Opéra national de Bordeaux Prize.

He returned to the Opéra de Lausanne to sing the Husband (Les Mamelles de Tirésias), Valentin (Faust) and the title role in Hamlet. He has also sung Karnac (Le Roi d’Ys) at the Opéra de Saint-Étienne, Sharpless (Madama Butterfly) at the Opéra de Reims and Escamillo (Carmen) at the Opéra de Rennes, and has appeared at the opera houses of Montpellier (Sparck in Fantasio), Tours (Papageno in The Magic Flute), Marseille (Phanor in La Reine de Saba, the title role in Eugene Onegin, Danilo in The Merry Widow), Reims (Papageno) and Metz (Ourrias in Mireille), at the Deutsche Oper Berlin (Hoël in Dinorah, ou Le Pardon de Ploërmel), at the Opéra de Lausanne (the title roles in Werther and Davel) and at the Glyndebourne Festival (the Husband).

In the 2024–2025 season his roles include Le Dancaïre (Carmen) at the Teatro di San Carlo in Naples and Brétigny in Manon at the Opéra de Paris.