Jaak-Nikolaas Lemmens (1823–1881) was a Belgian composer and conductor, primarily associated with the classical and sacred music genres. He was born in the region of Flanders and became known for his contributions to choral and organ music, as well as his role in the development of music education in Belgium. Lemmens studied at the Royal Conservatory of Brussels and later became a significant figure in the promotion of music in the liturgical context, often composing works for church services. His notable works include "Messe de la Trinité," a setting of the Mass that reflects his deep-rooted connection to sacred traditions. Additionally, he published a variety of organ pieces that are still appreciated for their technical demands and melodic charm. Lemmens' impact on music is evident in his advocacy for the integration of music education in religious institutions and his efforts to elevate the status of choral and organ music in Belgium. His teachings and compositions influenced a generation of musicians, ultimately contributing to the evolution of sacred music and the establishment of music as a vital component of Belgian cultural identity.