Machaeranthera is a genus of North American flowering plants in the family Asteraceae which are known by the common name tansyaster.

Several species easily hybridize with each other, as well, making identification difficult.

In general, members of the genus may be identified by the sharp-pointed, dagger-shaped anthers in the disc florets at the center of the flower.

The flower heads are usually daisylike, and are usually a shade of purple or blue, but may be pink, yellow, or white.

[4] The genus Machaeranthera is distinguished from the genus Dieteria by having once- or twice-pinnate leaves, whereas Dieteria has entire to toothed leaves.