Brodiaea filifolia is a species of flowering plant in the cluster-lily genus known by the common name threadleaf brodiaea. It is endemic to southern California, mostly in the region around the junction of Orange, Riverside, and San Diego Counties, where it is a resident of scattered remaining vernal pool and grassland habitats. It is a federally listed threatened species and it is listed as an endangered species on the state level. It is a perennial producing an flower cluster 20 to 30 centimeters tall which bears bright purple flowers. Each flower has six spreading petals 1 to 1.5 centimeters long with a center containing three stamens and narrow or small staminodes, which are flat sterile stamens lying against the petals.