The congressional Committee on Oversight and Government Reform has launched a formal investigation into Wikipedia following reports of systematic campaigns designed to “inject bias” into the online encyclopedia’s entries, particularly those related to Israel. 

The committee’s chairman, James Comer, and Representative Nancy Mace announced the probe on Wednesday in a letter sent to the head of the non-profit that hosts Wikipedia, the Wikimedia Foundation. Ms. Mace chairs the House Subcommittee on Cybersecurity, Information Technology, and Government Innovation. 

The lawmakers called on the Wikimedia Foundation’s chief executive, Maryana Iskander, to produce documents concerning volunteer editors who violated Wikipedia’s content policies, as well as detailed records of the platform’s enforcement mechanisms for addressing “intentional, egregious, or highly suspicious patterns of conduct on topics of sensitive public interest.”

The Wikimedia Foundation responded by acknowledging receipt of the congressional request and issuing a statement saying: “We welcome the opportunity to respond to the Committee’s questions and to discuss the importance of safeguarding the integrity of information on our platform.”

Wikipedia faces growing accusations of political bias, particularly in articles covering the Israel-Palestine conflict. Mr. Comer and Ms. Mace referenced in their letter two studies that “have highlighted efforts to manipulate information on the Wikipedia platform for propaganda aimed at Western audiences.” 

The first study, conducted by the Anti-Defamation League, “raised troubling questions” regarding an orchestrated campaign to embed antisemitic narratives, anti-Israel bias, and misleading information into Wikipedia entries about Israel and the broader Israel-Palestine conflict.

The ADL report, which was published in March 2025, uncovered a multiyear campaign conducted by at least 30 “bad-faith editors” who systematically circumvented Wikipedia’s policies to amplify criticisms of Israel while minimizing coverage of Palestinian terrorist violence and antisemitism. According to the findings, these coordinated anti-Israel activities significantly intensified following Hamas’s October 7 attack.

The ADL also cited evidence of pro-Hamas and extremist content embedded within Arabic-language Wikipedia pages, indicating that the platform’s neutrality standards may not be consistently enforced across non-English versions of the site.

The lawmakers also cited an investigation into a Russian-backed operation designed to distort Wikipedia entries with pro-Kremlin, anti-Ukraine, and anti-Western messaging. The sophisticated strategy employs a network of fraudulent news portals created by Russian operatives that masquerade as authoritative sources on Wikipedia and other platforms referenced by popular large language models.

To assist with the investigation, Mr. Comer and Ms. Mace have requested that Wikipedia produce six categories of materials before September 10, 2025. These include documents and communications that may point to coordination by nation-state actors or academic institutions to influence Wikipedia content, records from Wikipedia’s internal arbitration committee that resolves editorial disputes, and comprehensive documentation of Wikipedia’s policies for ensuring neutrality and addressing systematic bias.

The letter was received warmly by the Anti-Defamation League, which thanked Mr. Comer for “his leadership efforts to address this hate.” The advocacy group added: “As our research showed earlier this year, antisemitism and anti-Israel bias on Wikipedia are a significant problem.”

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Correction: March 2025 is when the ADL report about Wikipedia was published. An earlier version misstated the month.