Hypostomus yaku is a species of South American armoured catfish from the family Loricariidae. It is only known from the Rio Quente, a small thermal stream in the Rio Paranaíba drainage of the upper Paraná basin, Brazil. H. yaku is unusual when compared to other species of Hypostomus in that it tolerates warm water up to 34 °C and only attains a relatively small size, growing to 70.8 mm SL.