IronLisp was an implementation of the Lisp programming language targeting the Microsoft

Microsoft

Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...

 .NET framework

.NET Framework

The .NET Framework is a software framework that runs primarily on Microsoft Windows. It includes a large library and supports several programming languages which allows language interoperability...

. It was announced by Xacc.ide on July 23, 2007. It was superseded by IronScheme

IronScheme

IronScheme is an implementation of the Scheme programming language targeting the Microsoft .NET framework. IronScheme is a complete rewrite of IronLisp, incorporating lessons learnt while developing IronLisp....

 November 5, 2007 while still in beta. No further development will take place on IronLisp.

IronLisp Beta versions have been released under the Microsoft Public License.