Supporters of Fouad al-Farhan had campaigned for his release
A popular Saudi blogger who was detained by the authorities in December has been set free.
Fouad al-Farhan had used his website to criticise alleged corruption and call for democratic reforms in his country.
No official explanation was given for either the detention or the decision to free him.
Mr Farhan's detention had sparked protests from fellow bloggers. International human rights groups had been campaigning for his release.
Unlike most bloggers in Saudi Arabia, he wrote under his real name.
He used the blog to expose problems in Saudi society and campaigned on behalf of jailed Saudi liberals.
Correspondents say the whole affair surrounding the arrest Mr Farhan is part of a wider internet phenomenon issue in the Arab world.
With most governments in the region tightly controlling the activities of the official media, young people are increasingly turning to the internet to express dissent.