Haplopappus lyallii Tonestus lyallii is a species of flowering plant in the family Asteraceae known by the common names Lyall's goldenweed,[1] Lyall's serpentweed and Lyall's tonestus.

It is native to western North America, particularly in the Rocky Mountains and the mountain ranges of the Pacific Northwest with scattered occurrences between.

It is a perennial herb growing in clumps or short bunches not more than about 15 centimeters tall, the stem branching from a tough caudex.

The leaves are smooth-edged and linear or lance-shaped, the largest at the base of the plant reaching up to about 8 centimeters long.

The inflorescence is a single flower head or a pair of heads each about a centimeter wide with green or red phyllaries.