Eryngium pinnatisectum is an uncommon species of flowering plant in the carrot family known by the common name Tuolumne eryngo, or Tuolumne button celery. It is endemic to California, where it is known from the eastern Central Valley and adjacent Sierra Nevada foothills. It is a plant of vernal pools and similar wet habitat in the hills and grasslands. This is an erect perennial herb growing up to half a meter tall with a thick, hairless pale green branching stem. The greenish-white leaves are long and very narrow, lance-shaped with several sharp lobes, reaching 30 centimeters long. The inflorescence is an array of spherical flower heads, each surrounded by sharp-pointed, narrow bracts with thickened edges. The pale greenish flowers in the globelike head bloom in white petals.