Boechera fecunda (syn. Arabis fecunda) is a species of flowering plant in the mustard family known by the common names Mt. Sapphire rockcress and bitterroot rockcress. It is endemic to Montana in the United States, where there are twenty known occurrences in three counties. Threats to the species include the noxious weed Centaurea maculosa, spotted knapweed. The weed has a negative effect on rockcress populations, reducing seedling establishment. Livestock are another threat, trampling the land and facilitating the introduction of weeds. Mining activity is another threat.