Wyethia longicaulis is a species of flowering plant in the family Asteraceae known by the common name Humboldt mule's ears.

It is endemic to California, where it occurs in the North Coast Ranges and the Klamath Mountains.

It is a perennial herb growing from a tough taproot and caudex unit and producing a stem up to half a meter tall.

The inflorescence is usually a cluster of 2 to 4 flower heads, each with up to 10 yellow ray florets which may be up to 3 centimeters long.

The fruit is an achene about a centimeter long, including its tiny pappus.