Carolus Hacquart was a composer, born c. 1640 in Bruges, Belgium. Around 1670 he moved to the northern Netherlands, where he became active as a composer, teacher and an organiser of concerts. Hacquart is the composer of the first opera in the Dutch language De triomferende min. Unfortunately most of the music of this opera has to be considered lost.
Three other publications of his music have survived, his opus primum: Cantiones Sacrae (religious pieces for vocal soloists, choir and instrumentalists, 1674), his opus secundum: Harmonia Parnassia (collection of ten sonatas for two or three violins and basso continuo, 1686), and his third opus: Chelys (sonatas for the viola da gamba, probably originally with basso continuo, also very well playable without). These works are preserved in the library of Durham Cathedral, England.
Hacquart died, possibly in 1701, according to New Grove.