Using unbiased high-throughput sequencing for metagenomic screening of viruses in diseased tomato plants, we identified a viral complex that includes viruses previously reported in tomato crops on La Réunion Island as well as a novel polerovirus, tentatively named "tomato necrotic yellowing virus" (ToNYV, proposed species, "Polerovirus ToNYV"). Molecular characterization and phylogenetic analysis revealed that ToNYV is closely related to two recently described poleroviruses from Africa and the Middle East, one of which is transmitted by the whitefly Bemisia tabaci, a trait uncommon among poleroviruses. Our transmission experiments demonstrated that ToNYV is also transmitted by B. tabaci and is prevalent across major tomato-growing regions of La Réunion. These findings highlight the value of metagenomic virome analysis in diseased plants for identifying novel viruses potentially involved in emerging plant diseases, either individually or as components of viral complexes.