Jakob Hassler (c. 1564 – 1612) was a German composer and music theorist of the late Renaissance period. He is primarily known for his contributions to sacred music, particularly motets and hymns, which reflect the stylistic transition between the Renaissance and early Baroque periods. Hassler’s works often feature intricate polyphony and are characterized by their expressive melodies and harmonic innovations. Notable compositions include his collection of motets published in "Musicae Sioniae" and several settings of the chorale "Es ist das Heil uns kommen her." His music was influential in the development of Protestant church music during a time of significant religious change in Europe. Hassler's impact on music can be seen in his ability to blend traditional polyphonic techniques with emerging styles, paving the way for future composers in the German-speaking world. His theoretical writings also contribute to the understanding of music during this transitional period. Although not as widely recognized as contemporaries like Johann Sebastian Bach, Hassler's work laid important groundwork for the evolution of choral music.