It was the second time Turkey banned the site because of clips deemed disrespectful to Mustafa Kemal Ataturk. It is illegal in Turkey to insult the revered figure, whose portrait still hangs in nearly all government offices nearly 70 years after his death.
Users trying to access the Web site from Turkey were met with notices in English and Turkish saying it was banned under an Ankara court order issued Jan. 17.
Last March, another court blocked access to YouTube for two days after a complaint that some clips insulted Ataturk, a war hero who founded Turkey from the ruins of the Ottoman Empire. The ban was lifted after YouTube removed the offending videos.
In September, a court in the eastern city of Sivas ordered a ban after saying video on the site insulted Ataturk, President Abdullah Gul, Prime Minister Recep Tayyip Erdogan and the army, but the ban was never implemented.
It was not clear how long the current ban would last. The state-run Anatolia said officials from YouTube, which is owned by Google, issued a statement saying the company hoped access would be re-established quickly.
The YouTube bans in Turkey have highlighted the country's troubled record on free expression. Several prominent Turkish journalists and writers — including Nobel literature prize winner Orhan Pamuk — have been tried for allegedly insulting "Turkishness."
Turkey is not alone in blocking YouTube. Last year, the Thai government banned the site for about four months because of clips seen as offensive to Thailand's revered monarch, King Bhumibol Adulyadej.
And in May, Moroccans were unable to access YouTube after users posted videos critical of Morocco's treatment of the people of Western Sahara, a territory that Morocco took control of in 1975. An official blamed a technical glitch, but could not explain its nature or why it affected only the YouTube site.