Esterel is a synchronous programming language for the development of complex reactive systems. The imperative programming style of Esterel allows the simple expression of parallelism and preemption. As a consequence, it is very well suited for control-dominated model designs.

The development of the language started in the early 1980s, and was mainly carried out by a team of Ecole des Mines de Paris and INRIA lead by Gérard Berry. Current compilers take Esterel programs and generate C code or hardware (RTL) implementations (VHDL or Verilog).

The language is still under development, with several compilers out. The commercial version of Esterel is the development environment Esterel Studio. The company that develops it (Esterel Technologies) has initated a normalization process with the IEEE. The Esterel v7 Reference Manual Version v7 30 – initial IEEE standardization proposal is publicly available.