Unrest in the tiny island state started on 14 February 2011 and has left at least 40 people dead.
It made headlines because of Bahrain's status as a key US ally, its sectarian divide and its previously stable image.
Predominantly Shia Muslim protesters have been demanding action to tackle economic hardship, the lack of political freedom and employment discrimination in favour of the ruling Sunni Muslim minority.
Bahrain, home of the US Fifth Fleet, like Iraq, is one of the few Arab states with a Shia majority and, as such, is seen by some as vulnerable to influence from Iran.
The government, led by King Hamad bin al-Khalifa, has accused Tehran of orchestrating the protests.
For weeks in early 2011, the demonstrators occupied the centre of the capital, Manama.
King Hamad clamped down hard on 16 March, clearing the protesters' camp in a show of force condemned by the UN as "shocking".
He imposed a state of emergency and used hundreds of soldiers from Saudi Arabia and the United Arab Emirates to beef up security.
The state of emergency was lifted on 1 June in an apparent attempt to signal that the island was returning to normal.
However, security measures remain in place to stop large gatherings and the authorities have continued to use force to break up small protests in Shia villages.
Rights groups say the government has detained more than 1,600 people - including human rights activists, doctors, bloggers and opposition supporters - since the unrest started.
In April 2011, four demonstrators were sentenced to death in closed-door trials and three others to life in prison for the killing of two police officers during protests.
Forty-seven doctors and nurses who treated some of the wounded protesters went on trial, accused of disseminating false information about the casualties and attempting to topple the monarchy.
In September 2011, an emergency military court found 20 medics guilty of publicly inciting "hatred and contempt", as well as engaging in illegal assemblies. But on 14 June an appeals court partially overturned the ruling, acquitting nine doctors and reducing the sentences of nine others. Two others are thought to have fled Bahrain and are in hiding.
In November an independent commission published a report stating that "excessive force" had been used when the government crushed the protests. The report stated that detainees had been blindfolded, whipped, kicked, given electric shocks and threatened with rape to extract confessions.
King Hamad expressed "dismay" at the findings and promised reforms to prevent abuses by the security forces.
However, analysts say progress on implementing reforms has been slow and human rights groups say torture is still used by the security forces.
Protests have continued into 2012, including around the controversial Bahrain Grand Prix in April. The political climate has shown signs of becoming increasingly polarised in recent months.
Bahrain's most prolific activist is probably Abdulhadi al-Khawaja, an outspoken critic of the government who was handed a life sentence last year. He went on hunger strike in January 2012 for 110 days. He ended the hunger strike in May but remains in jail.