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Background The genetic myopathies are a large, clinically and genetically heterogeneous group of disorders caused by variants in >300 genes. Many patients with genetic myopathies remain undiagnosed even after use of current clinical genetic testing modalities (e.g. next-generation sequencing, etc.). Long-read sequencing (LRS) is a newer sequencing approach that has several technical advantages over existing sequencing methodologies, potentially allowing for improved diagnostic rates. We aimed to explore the diagnostic utility of Oxford Nanopore LRS in the genetic myopathies.Methods Individuals with either a genetically solved myopathy (n = 17; Group A) or a suspected genetic myopathy that remained genetically unsolved or incompletely solved following standard clinical genetic testing (n = 28; Group B) were recruited from patients referred to the Concord Hospital Neuromuscular Clinic and the NeuRA Clinics. Blood was collected and sequenced using an adaptive sampling Oxford Nanopore LRS panel targeting 333 myopathy genes/loci.Results The Oxford Nanopore LRS panel detected all previously identified causative variants in Group A and led to a new genetic diagnosis in 21.4% (6/28) of cases from Group B, with pathogenic variants identified in LAMA2, the 4q35 D4Z4 repeat array and several oculopharyngodistal myopathy (OPDM) genes (GIPC1, NOTCH2NLC, RILPL1, ABCD3).Conclusion LRS provided a streamlined approach to identifying a range of different pathogenic variants and led to resolution of a significant proportion of our previously undiagnosed genetic myopathy cohort. In particular, we identified a number of recently described pathogenic short tandem repeat expansions in OPDM genes for which clinically accredited genetic testing is not currently available in Australia.