Jacobaea aquatica or Senecio aquaticus, the water ragwort or marsh ragwort, is a plant of the Asteraceae family. It is a perennial or biennial plant: young plants form a rosette near the ground, eventually producing a taller flowering shoot with many bright yellow flower heads, each with prominent ray florets. It grows in damp, grazed grassland, especially where there has been some disturbance.