Nine of the 10 men are in solitary confinement.
Those on protest fast are demanding that the government grant the prisoners fair and public trials or set them free.
Mohammad Fahad Al-Qahtani, a college professor and one of the activists on hunger strike, told Al Jazeera that they had decided on the protest as a last resort. He said that their petitions seeking fair trials for the men and for improving conditions in jails had gone unheeded.
He said that freedoms of expression and assembly were not present in Saudi Arabia.
"So that is really the case. It is not a matter of speaking out, it is a matter of advocating human rights.
The 11 detainees include a former judge and ex-university professors.