(1930-2002)
Edsger W. Dijkstra, Dutch computing scientist.
https://web.archive.org/web/20200825231922/http://www.virtosphere.de/schillo/teaching/WS2001/Photos/Dijkstra.jpg
If you don't know him, read his books and articles. Also read Beauty Is Our Business.
See archive 
for an autobiography including his contributions to the development of compilers, and his run-in with Harry D. Huskey, inventor of the SWAC.
See also www.cs.utexas.edu – UT Computer Sciences Department's Obituary.
EWD Archive is at www.cs.utexas.edu .
As a skilled writer and a master of language Dijkstra is the source of many memorable sayings, some of which are now consecrated as integral parts of the computer science lingo. The quotes which inspired or otherwise interested wikizens are on a separate page Ew Dijkstra Quotes
Links and Papers
en.wikipedia.org Wikipedia
www.cs.utexas.edu University of Texas Austin Faculty Page
www.cbi.umn.edu Collected Papers
luke.acm.org ACM Citation
www.cs.utexas.edu Online versions (PDF) of collected manuscripts
"On the T.H.E. Operating System", which not only described the classic operating system design, but in a brief appendix describes semaphores. (see www.cs.utexas.edu )
One of my favorites is his Turing Award lecture The Humble Programmer. -- June Kim
Guidance on how to say his name moved to Pronouncing Dutch.
See also: Answers To Questions From Students Of Software Engineering, Goto Considered Harmful, Dining Philosophers
See original on c2.com