Monolopia congdonii (formerly Lembertia congdonii) is a rare species of flowering plant in the family Asteraceae known by the common name San Joaquin woollythread.

[1] It is endemic to California, where it is known only from the southern San Joaquin Valley and one area in nearby Santa Barbara County.

This is a small annual herb with a trailing or somewhat upright stem coated thinly in woolly fibers.

The inflorescences at the end of stem branches bear small hemispheric flower heads.

Each is about half a millimeter long and has a minutely lobed tip.