Spanish; Castilian: italics=unset|Quien Sabe Valley, originally known as Spanish; Castilian: Cañada de Quién Sabe, is a valley in the Diablo Range in San Benito County, California. It runs from its mouth, at an elevation of 1572abbr=offNaNabbr=off, to its head at 36.8961°N -121.2122°W at an elevation of 1800abbr=offNaNabbr=off. The valley is drained by Quién Sabe Creek, ultimately a tributary to the Pajaro River to the northwest.
Quien Sabe Valley is the location of the Rancho Santa Ana y Quién Sabe.