Caltha is a genus of rhizomatous perennial flowering plants in the family Ranunculaceae, to which ten species have been assigned. They occur in moist environments in temperate and cold regions of both the Northern and Southern Hemispheres. Their leaves are generally heart-shaped or kidney-shaped, or are characteristically diplophyllous. Flowers are star shaped and mostly yellow to white. True petals and nectaries are missing but the five or more sepals are distinctly colored. As usual in the buttercup family there is a circle of stamens around free carpels.

Ranunculaceae is a family of over 2,000 known species of flowering plants in 43 genera, distributed worldwide.