The foundation that runs Wikipedia said Thursday it had filed a lawsuit with the European Court of Human Rights to lift Turkey's two-year block on the website.
Turkey blocked all access in April 2017 over entries the government said linked Turkish authorities to terrorist activities.
Wikimedia Foundation, a non-profit organisation, said the ECHR application follows attempts to lift the ban through local courts, speaking to Turkish officials and campaigns to put pressure on Ankara to allow access.
"The Wikimedia Foundation has filed suit against Turkey in the (ECHR)," Katherine Maher, executive director of Wikimedia Foundation, told reporters in a telephone briefing, a decision that she said was "not made lightly".
While lower Turkish courts upheld the ban, Turkey's constitutional court has not given any response to the Wikipedia case in two years, Wikimedia said in a statement.
The foundation sees the ban as a violation of rights including freedom of expression, guaranteed by Article 10 of the European Convention.
The issue began over two English-language pages on state-sponsored terrorism and the Syrian civil war that Ankara believes falsely linked it to terrorist activities.
Stephen LaPorte, Wikimedia Foundation's legal director, said the government demanded the pages' removal "without any official explanation of what part is allegedly illegal".
Maher said the foundation did not comply with Turkey's request to remove the pages because "we believe that the content in question was legally-protected free expression".
Turkey has over the past few years temporarily blocked access to social media websites such as Facebook and Twitter after events including mass protests or terror attacks.
China this month broadened its block of Wikipedia to include all language editions, becoming the only other country after Turkey to do so. Most editions of the online encyclopaedia except the Chinese language version were available previously.
Maher said Wikimedia was exploring ways to lift the block in China as well.