Sh2-135 is a visible emission nebula in the constellation Cepheus.
It is located in the southern part of the constellation, north of the line connecting the stars ζ Cephei and δ Cephei.
It is an H II region connected to a dark nebula of interstellar dust, which has a distinct and expanding ionization front. A model that can explain the situation well is the so-called blister model: according to this scheme, the ionized gas is swept away from the ionization front by the interaction between the H II region and the adjacent molecular cloud. The star responsible for the ionization of the gas has the spectral class O9.5V; the distance estimates give a value of about 1900 parsecs (about 6200 light years). Around this nebula, IRAS has identified numerous sources of infrared radiation, indicating the presence of more recent star formation processes