Monardella frutescens is a rare species of flowering plant in the mint family known by the common name San Luis Obispo monardella. It is endemic to California, where it is known only from the sand dunes and scrub on the coastline of San Luis Obispo and Santa Barbara Counties. It is a perennial herb producing several purple stems. The thin, narrow, wavy-edged leaves are 1 to 5 centimeters long and borne in clusters along the stem. The flower cluster is a head of several flowers blooming in a cup of papery purplish to straw-colored leafs. The flowers are purple to pink in color. This species sometimes hybridizes with its relative, Monardella crispa, which shares its habitat.