Abstract Body: Visceral myopathy is a severe and often fatal disorder driven by dysfunction of gastrointestinal (GI) smooth muscle cells (SMCs), leading to chronic intestinal pseudo-obstruction and profound impairment of gut motility. Despite its clinical significance, the molecular pathways that preserve visceral SMC identity and contractile function remain incompletely understood. Ubiquitin-dependent protein regulation governs numerous cellular processes by controlling protein stability and activity, yet its contribution to visceral SMC homeostasis has received little attention. In this study, we identify the E3 ubiquitin ligase ARIH1 as a previously unrecognized regulator of visceral SMC function and gastrointestinal motility. ARIH1 is widely expressed across tissues, and integrative analyses of human and murine transcriptomic datasets revealed aberrant ARIH1 expression in degenerating visceral SMCs associated with visceral myopathy. SMC-specific deletion of Arih1 via Myh11^Cre caused profound gastrointestinal dysfunction, including intestinal pseudo-obstruction, marked dilation of the GI tract, and severe dysmotility of the cecum and colon, culminating in early postnatal lethality at approximately four weeks of age. Comprehensive phenotypic analyses—including histopathology, gastrointestinal transit measurements, and ex vivo muscle contractility assays—demonstrated extensive bowel dilation, increased fibrosis, disrupted elastin architecture, delayed transit, and impaired smooth muscle contractile performance in Arih1-deficient mice. Transcriptomic profiling of the muscularis layer uncovered a marked phenotypic switch toward a synthetic SMC state, with enhanced extracellular matrix gene expression and suppression of canonical contractile markers. Concordantly, ARIH1 knockdown in primary human colonic SMCs reduced contractile gene expression and attenuated contractile capacity. Collectively, these findings establish ARIH1 as an essential determinant of visceral SMC contractile integrity and gastrointestinal motility and implicate dysregulated ubiquitin signaling as a potential pathogenic mechanism in visceral myopathy. This work highlights the need for further investigation into ubiquitin-mediated pathways in smooth muscle–driven gastrointestinal diseases.