The present invention provides an actinic ray-sensitive or radiation-sensitive resin composition that can provide a resist film with excellent sensitivity and a pattern with excellent LER performance, and can suppress pattern collapse during pattern formation. In addition, the present invention also provides a resist film, a pattern forming method, a mask blank with a resist film, a method for producing a photomask, and a method for manufacturing an electronic device, each using the actinic ray-sensitive or radiation-sensitive resin composition. The actinic ray-sensitive or radiation-sensitive resin composition of an embodiment of the present invention includes a resin X having a repeating unit A represented by General Formula (I), a repeating unit B having an acid-decomposable group, and a repeating unit C selected from a repeating unit c1 represented by General Formula (II) and the like; a compound Y which is a basic compound or ammonium salt compound whose basicity is reduced upon irradiation with actinic rays or radiation; and a photoacid generator Z which is a compound other than the compound Y.