Classically entropy is defined for measure-preserving actions and continuous actions of countable amenable groups. The class of sofic groups includes all discrete amenable groups and residually finite groups. In 2008 Lewis Bowen defined entropy for measurepreserving actions of countable sofic groups, under the condition that the underlying space has generating partitions with finite entropy. I will give a definition of entropy for all measure-preserving actions and continuous actions of countable sofic groups, and discuss some properties of this entropy. Although the definition is in the language of dynamical systems, the proof for the well-definedness uses operator algebras in a fundamental way.