Iris tenuissima is a species of iris known by the common name longtube iris.
It is endemic to California, where it is a common wildflower in the woodlands and forests of the northern part of the state.
This rhizomatous perennial herb produces narrow leaves and an erect inflorescence bearing two iris flowers. The flower has a long tubular throat which may exceed 5 centimeters in length before it opens into white, purple, or reddish-brown streaked tepals.