SM4, Sm4 or SM-4 may refer to:
Technology and engineering SM4 (cipher), a block cipher used in the Chinese National Standard SM-4, minicomputer VR Class Sm4, a type of train operated by the VR Group HST-SM4, the final servicing mission to the Hubble Space Telescope Standard Missile 4, a missile
Other uses SM4 (classification), a swimming classification SM4, a part of the SM postcode area, in Sutton, England