Helmholtz resonators have long been essential for acoustic control, enhancing or nullifying sound at specific frequencies. Traditionally, these resonators are effective for fixed-frequency applications, but lose efficacy if the excitation frequency changes. This paper presents the first tunable broadband origami-based Helmholtz resonator, featuring a compliant origami design with auxetic properties for optimal volume variation. Multiphysics simulations determined the adaptive cavity geometry, and experimental tests validated the models, showing high tunability (up to 25% around a central frequency of 461 Hz with a 95% absorption rate) and broad bandwidth (up to 13% around the central frequency with a 95% absorption rate) with minimal geometry variation (8 mm in diameter). This work marks a significant advancement over traditional Helmholtz resonators.