The rapid progress of artificial intelligence (AI) and the internet of things (IoT) has driven growing demand for high-performance, skin-compatible vibration sensors capable of capturing subtle physiological and environmental signals. Low-dimensional materials offer unique advantages in sensitivity and flexibility, yet challenges remain in achieving high strain responsiveness, mechanical robustness, and large-area uniformity. Here, we report an ultrasensitive, low-profile, and stretchable vibration sensor based on large-area single-layer molybdenum disulfide (MoS2) ribbon networks (SLRNs) grown via a vapor-liquid-solid mechanism. Embedding SLRNs within a thermoplastic elastomer [styrene-ethylene-butylene-styrene (SEBS)] yields record-high sensitivity among MoS2-based sensors, with gauge factors up to 5300 at <1.6% strain. This response arises from nanocrack-mediated electron transport induced by the thermal expansion mismatch between MoS2 and SEBS. The ~6-micrometer-thick sensors detect vibrations and acoustic signals over a wide frequency range (>500 hertz), enabling deconvolution of complex stimuli. This work establishes a path toward ultrathin, ultrasensitive wearable sensors for health care and robotic applications.