Wikipedia is taking Turkey to the European Court of Human Rights (ECHR) over a two-year ban imposed on the site in the country.
The Wikimedia Foundation says it filed the petition on the grounds that a ban on its online encyclopaedia violated the right to freedom of expression.
Access to Wikipedia has been blocked in Turkey since April 2017.
Officials said at the time that "an administrative measure" had been taken, but gave no reason for the ban.
Turkish media said authorities had asked Wikipedia to remove content by writers "supporting terror".
"We are taking this action as part of our continued commitment to knowledge and freedom of expression as fundamental rights for every person," the Wikimedia Foundation, the non-profit organisation which runs Wikipedia, said in a statement.
"We are doing so only after continued and exhaustive attempts to lift the block through legal action in the Turkish courts, good faith conversations with the Turkish authorities, and campaigns to raise awareness of the block and its impact on Turkey and the rest of the world."
More than two years on, it still happens: I do a quick internet search on a topic, which leads to a Wikipedia link. I click on it, without thinking. Error 404: Page not found. Ah yes, a country aiming to join the European Union has banned a free encyclopaedia website.
Turks have found ways to circumnavigate the block, using "mirror" Wikipedia URLs or Virtual Private Networks (VPN) to change their IP location. But it's still a hindrance to many.
Ankara complained about the content of two articles: on the Syrian war and on state-sponsored terrorism, demanding they be removed. In meetings with the Turkish authorities, Wikipedia bosses explained that articles could be edited - and that removing them contravened values of democratising knowledge.
Referral to the ECHR, Wikipedia told me, sends an important message on free speech. But the court has ruled against Turkey more than any other country - and Ankara routinely ignores verdicts, paying fines instead. This one could go the same way.
Wikipedia's founder, Jimmy Wales, said the site would keep pressing its case.
Turkey has temporarily blocked social media sites including Facebook and Twitter in the past, usually following protests or terrorist attacks.
Prior to the ban, more than 300,000 articles had been published in Turkish on the Wikipedia site.
The ECHR is an international court based in Strasbourg which was set up to uphold the European Convention on Human Rights after World War Two.