Piet Beertema (born 22 October 1943 in Amsterdam) is a Dutch Internet pioneer. On November 17, 1988 at 14:28 hours, he linked the Netherlands as the second country (after the United States) to NSFnet, a precursor to the Internet. Beertema was then working as an administrator at the Centrum Wiskunde & Informatica (CWI) in Amsterdam.
His first job was in 1965 at the Dutch National Aerospace Laboratory, where he first came into contact with a computer (an Elliott 803-B). In 1966 he joined the Center for Mathematics and Computer Science, where he worked until his retirement.
On April 1, 1984, Beertema was responsible for the first April Fools' Day hoax on the internet. Posing as "Chernenko" of the Moscow Institute for International Affairs, he posted a message on the Usenet network. This greeted fellow users of Usenet on behalf of the Soviet Union. He further stated that one aim of them joining was to better present the views of the Soviet regime, alleging that the American administration were seeking war and world domination. Beertema used the ID "Kremvax", which was subsequently used by Vadim Antonov in 1991, when he did actually become the first Moscovite site to join usenet. However many people assumed this was another joke.
On April 25, 1986 Beertema recorded the first country code top level domain .nl. In 1996 he co-founded the Foundation for Internet Domain Registration Netherlands that would take over the management of the .nl domain, after doing this himself for almost 10 years.
On June 9, 1999 he received a royal decoration, Knight of the Order of the Dutch Lion. On September 16, 2004 he officially retired.
- van Ringelestijn, Tonie (2008-11-17). "20 jaar internet in Nederland en Europa". WebWereld (in Dutch). IDG Nederland. Retrieved 2011-01-24.
Op 17 november 1988, om half drie 's middags, ontving systeembeheerder Piet Beertema van het CWI in Amsterdam het historische e-mailtje waarin stond dat het CWI, als eerste instelling buiten Amerika, was verbonden met NSFnet.
- Schonfeld, Zach. "'Kremvax': The Strange Story of the Internet's First April Fools' Prank". Newsweek. Newsweek LTD. Retrieved 5 April 2016.
- (in Dutch)  (Onze mijlpalen), Official website of SIDN