Provided are a lens and a lens assembly including a lens barrel defining a receiving space and provided with a light-through hole and the lens received in the receiving space. The lens includes an optical portion for imaging and a peripheral portion provided with through holes penetrating through the peripheral portion along an optical axis of the lens. The through holes are distributed on circumferences of different diameters, centers which are located on the optical axis. The farther the circumference is from the optical axis, the more through holes are arranged on the circumference. When light enters regions of the lens where the through holes are arranged, stray light is absorbed, effectively reducing the reflection of the stray light at the peripheral portion and improving imaging quality. The through holes do not affect assembly accuracy of the lens and reduce appearance yield of the lens or increase cost.