We discovered a giant magnetoelasticity in soft matter with up to 5-fold enhancement of magnetomechanical coupling factors compared to that of rigid metal alloys without an externally applied magnetic field. A wavy chain analytical model based on the magnetic dipole-dipole interaction and demagnetizing field was established, fitting well to the experimental observation. To explore its potentials in electronic textiles, we coupled it with magnetic induction to invent a textile magnetoelastic generator (MEG), a new working mechanism for biomechanical energy conversion, featuring an intrinsic waterproofness, an ultralow internal impedance of approximately 20 Ω, and a high short-circuit current density of 1.37 mA/cm2, which is about four orders of magnitude higher than that of other textile generator counterparts. Meanwhile, assisted by machine learning, the textile MEG could continuously monitor the respiratory activities on heavily perspiring skin without any encapsulation, allowing a timely diagnosis of the respiration abnormalities in a self-powered manner. We foresee that this discovery can be extended to wide-range soft-matter systems, emerging as a compelling approach to develop electronic textiles for energy, sensing, and therapeutic applications.