Methods, systems, and apparatus, including computer programs encoded on computer-readable storage media, for providing action objects in a semantic graph. IN some implementations, semantic graph data indicates a semantic graph of objects and relationships between the objects. The semantic graph data defines an action object that represents an action that can be initiated, and the semantic graph data indicates a particular object type or a particular data type with which the action object can be used. An object of a particular object type or data of the particular data type is identified as being involved in processing of the one or more computers. In response to identifying the use of the object of the particular object type or data of the particular data type, an indication is provided that the action represented by the action object can be initiated.