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Andreesen, co-author of the first widely used Web browser, sits on board of directors for board of directors of Facebook, eBay, HP, and other U.S. tech companies.
"Obviously he's a traitor. If you look up in the encyclopedia 'traitor,' there's a picture of Ed Snowden," the Silicon Valley venture capitalist said. "He's a textbook traitor. They don't get more traitor than that."
The dictionary definition of "traitor" is "a person who betrays a country or group of people by helping or supporting an enemy."
Andreessen bases his views on that argument that the 30-year-old "stole nationals security secrets and gave them to everyone on the planet."
Snowden's stole hundreds of thousands of top secret NSA documents and fled to Hong Kong last May. Top U.S. officials claim that the stolen documents include U.S. military information that has little to do with civil liberties or privacy.
The former NSA systems administrator provided an estimated 200,000 documents to journalists, sparking a flurry of reports over the last year that exposed NSA surveillance practices in the U.S. and around the globe.
Andreessen noted that he is in the "distinct minority" in Silicon Valley, where the disclosures have led to calls for widespread reform of the relevant laws, and said he was surprised that so many people were shocked by the revelations.
"I think if you actually followed the NSA, read the books, followed the history … then you generally assumed that they were doing just about everything that has come out," he said. "We've been funding this agency for 50 years that has 10s of thousands of employees and 10s of billions of dollars. I thought they were spying. … I thought everybody knew that."
Stories based on the Snowden cache that have riled Silicon Valley include evidence of the widespread collection of "metadata" from U.S. phone calls as well as a program called PRISM that compels Internet companies to turn over any data that match court-approved search terms. Both are approved by Congress but have lacked strong oversight.
Other stories have included NSA surveillance abroad, including spying on German Chancellor Angela Merkel's non-encrypted phone, the leaders of Russia, the metadata of foreign populations, and various targets in China. Andreessen notes that a lot of that outrage is political.
"Some of the shock I think is fake," he said, adding that foreign governments like Germany and Russia "knew full well what was happening … and of course they do many or all of the same things themselves."
Andreessen described the potential damage to Silicon Valley as "very serious and very worrying," noting that U.S. tech companies are in danger of losing critical funding from abroad.
"Some companies get 70% of revenue outside the U.S.," Andreessen noted. "There's a big open question right now how successful they'll be when they sell products overseas. ... A lot of countries are jealous of Silicon Valley and will use the Snowden affair as an excuse to implement protectionist policies."
The leaks are already hurting business in Silicon Valley.
"It's clear to every single tech company that this is affecting their bottom line," Daniel Castro, a senior analyst at the Information Technology and Innovation Foundation who predicted that the U.S. cloud computing industry could lose $35 billion by 2016, told the New York Times in March.
Lastly, Andreessen was critical of the Obama administration's response to the leaks.
"The administration is … letting the NSA hang out to dry, they're letting the American tech industry out to dry. I haven't met anybody who feels like the White House has a plan, it's just happening."
Disclosure: Marc Andreessen is an investor in Business Insider.