Eiffel is an ISO-standardized, object-oriented programming language designed by Bertrand Meyer (an object-orientation proponent and author of Object-Oriented Software Construction) and Eiffel Software.

The design of the language is closely connected with the Eiffel programming method. Both are based on a set of principles, including design by contract, command-query separation, the uniform-access principle, the single-choice principle, the open-closed principle, and option-operand separation.