Wikipedia has been blocked in Pakistan for hosting "blasphemous content".
The move was announced on Saturday after the free online encyclopaedia was given a 48-hour deadline to remove some material.
The Pakistan Telecommunication Authority (PTA) said Wikipedia failed to comply with its ultimatum.
The Wikimedia Foundation, which hosts Wikipedia, said the ban meant Pakistanis would be denied access "to the largest free knowledge repository".
Blasphemy is a highly sensitive and incendiary issue in Pakistan.
Other platforms including Tinder, Facebook and YouTube were previously blocked in the Muslim-majority country.
PTA spokesperson Malahat Obaid said Wikipedia failed to respond to "repeated correspondence" over the removal of "blasphemous content".
"They did remove some of the material but not all," he added, confirming that the website would remain blocked until "all the objectionable material" was removed.
Details of the material in question have not been revealed.
The Wikimedia Foundation said if the ban continued it would "deprive everyone access to Pakistan's knowledge, history, and culture".
Free speech campaigners have raised concerns over the move, saying there seemed to be "a concerted effort to exert greater control over content on the internet".
"The main purpose is to silence any dissent," said digital rights activist Usama Khilji.
"A lot of times blasphemy is weaponised for that purpose," he added.
In 2010 Pakistan blocked YouTube because of its "growing sacrilegious content.
Facebook was blocked in 2010 following a row over an internet campaign inviting people to draw images of the Prophet Muhammad.
Dating apps including Tinder and Grindr were also previously banned for disseminating "immoral content".