Héloïse Gaillard is best known as the director of the early music group Ensemble Amarillis but also performs as a solo flutist and recorder player. Gaillard has been a member of several leading French early music ensembles.

Gaillard was born in Paris. Her sister is the Baroque cellist Ophélie Gaillard. Héloïse began her educational career as a recorder player, studying with Jean-Pierre Nicolas at a music school in Verrières le Buisson in the Paris suburbs. She also took classes in piano and harpsichord but decided that wind instruments were her main interest and added the oboe to her curriculum. Gaillard attended the Regional Conservatory of Tours (CNR) and earned a first prize in recorder there. Gaillard went on to the Rotterdam Conservatory, studying recorder with Han Tol and earning a soloist's diploma. She also earned a first prize in modern oboe at the CNR Tours, turning next to the Baroque oboe, which she studied at the Lemmens Institute in Louvain and finally the National Conservatory of Music and Dance in Paris (CNSMD), where she received a diploma in Baroque oboe. She also found time to earn a musicology degree from the highly competitive Sorbonne University in Paris.

In 1994, Gaillard, her sister Ophélie, and harpsichordist Violaine Cochard founded Ensemble Amarillis in Paris. They had been brought together at the conservatory there by harpsichordist and conductor Pierre Hantaï. The new group won major prizes in the middle and late '90s, including the first prize of the Early Music Competition of York, England, and, in 1997, the Sinfonia competition chaired by harpsichordist Gustav Leonhardt. Ensemble Amarillis has made more than 20 recordings and has attracted such guest directors as Ton Koopman, Jordi Savall, and Christophe Coin. As of the early 2020s, Gaillard remains the group's artistic director. She has also performed and recorded as a soloist, releasing an album of Telemann's Fantasies for solo flute on the Agogique label in 2013, and has performed as a member of Christophe Rousset's Les Talens Lyriques, Hervé Niquet's Concert Spirituel, and Emmanuelle Haïm's Le Concert d'Astrée, all top French early music groups. As a soloist or ensemble member, she has appeared in such major halls as the Théâtre des Champs Elysées in Paris, the Concertgebouw in Amsterdam, and the Philharmonie in Berlin, as well as at various summer festivals. In 2022, Gaillard and Ensemble Amarillis released an album of solo cantatas and instrumental works by Élisabeth Jacquet de la Guerre on the Evidence Classics label. Gaillard is often active as an educator, most recently teaching Baroque oboe at the National Conservatory of Music (CNSM) in Paris and at the Centre de Musique Baroque at Versailles palace. ~ James Manheim, Rovi