The dark-sided thrush (Zoothera marginata) is a species of bird in the thrush family Turdidae. It is also known as the lesser brown thrush, the long-billed ground-thrush, and the dark-sided ground-thrush. The species is monotypic (lacking subspecies) and is closely related to a number of thrushes in the genus Zoothera, including the long-billed thrush and the widespread scaly thrush. It was described by Edward Blyth in 1847 based upon a specimen collected in Rakhine in Burma (Myanmar).