Lee Daniel Crocker (born July 3, 1963) is an American computer programmer. He is best known for rewriting the software upon which Wikipedia runs, to address scalability problems. This software, originally known as "Phase III", went live in July 2002 and became the foundation of what is now called MediaWiki. MediaWiki's code repository was still named "phase3" until the move from Subversion to Git in March 2012. In June 2010, Crocker and others won the USENIX Advanced Computing Technical Association STUG award for contributions to the Wikipedia software.