Cloud computing has pulled in numerous business organizations and users because of its simplified administration effort, minimal maintenance cost and pervasive access to out-sourced resources, which can be hardware or software. Users share these resources in large-scale environments over the Internet. Stringent access control must be implemented in a cloud storage system for protecting sensitive information. Access control models in the current literature such as Discretionary Access control (DAC), Mandatory Access Control model (MAC), Role-Based Access Model (RBAC) or Attribute Access Control Model (ABAC) consider the entities of access control in isolation and thus leading to incorrect access control decisions. In this paper, Ontology-Based Access Control is proposed. This proposal uses an ontology to model the entities associated with access control and their interrelationships among them, which could be effortlessly adjusted to Cloud environments. Ontology promises to streamline knowledge sharing among the entities. Subsumption property is exploited over concepts, properties and individuals. The experimental results show that the number of rules to be stored in Policy Base is reduced and reasoning time is also considerably reduced because of applying subsumption property and hence access decision is made faster. Also, our work is compared with the existing works against the state of art models with the help of access control metrics provided by the National Institute of Standards and Technology (NIST). Our work answers the queries related to metric effectively than the existing works. Hence the performance of the system is increased and suitable for securing cloud data.