The non-profit behind Wikipedia, the Wikimedia Foundation, is suing the National Security Agency and the Department of Justice over a government surveillance program.
The suit challenges a program that collects data by tapping into the infrastructure, or backbone, the Web is built on.
"We are asking the court to order an end to the NSA's dragnet surveillance of Internet traffic," Wikipedia founder Jimmy Wales wrote in a New York Times opinion piece about the suit.
The Justice Department and the NSA did not immediately respond to a request for comment about the suit.
• Snowden files: Spy agency's cyber tactic revealed
• Snowden revelations: Nicky Hager and Ryan Gallagher: New Zealand's spy reach stretches across globe
• Cheryl Gwyn will tell me if GCSB breaks law on Kiwi spying - Key
The suit alleges that the government has been tapping into cables that are part of the Internet's infrastructure, a practice often called "Upstream" collection, which violates the First and Fourth Amendments, according to a blog post from Wikimedia.
Such programs have been targeted in other lawsuits, including the long-running Jewel v. NSA case, which was originally based on documents from a AT&T technician in San Francisco.
Some cases about government surveillance have either been thrown out or stalled after failing to prove they were specifically targeted by the government surveillance programs.
But that may be less of an issue for Wikimedia, which has based its case largely on information disclosed by NSA contractor Edward Snowden.
Some Snowden documents appeared to show that the government is tapping into cables that connect the United States to the rest of the online world.
One government slide disclosed by Snowden suggested that Wikipedia and its users were targeted as part of government surveillance programs, the lawsuit alleges.
However, there may be other legal hurdles.
Last month, Jewel v. NSA hit a significant roadblock when a federal judge sided with the government's state secret defence - ruling that the plaintiffs could not win their challenge over NSA tapping of the Internet backbone without disclosing information that would harm national security.
The type and amount of data collected as part of these programs are unclear.
But the data could reveal details about people's browsing history, scaring some from using the Internet freely, privacy advocates have argued.
"By tapping the backbone of the internet, the NSA is straining the backbone of democracy," Wikimedia Foundation executive director Lila Tretikov said in a blog post about the suit.
"Wikipedia is founded on the freedoms of expression, inquiry, and information.
"By violating our users' privacy, the NSA is threatening the intellectual freedom that is central to people's ability to create and understand knowledge."
The American Civil Liberties Union is representing plaintiffs in Wikimedia v. NSA, a group that includes Human Rights Watch, Amnesty International USA, Global Fund for Women, and The Nation Magazine among others.