The international rights group accuses the West, particularly Britain and the United States, of turning a blind eye to the abuses in the island kingdom.
Bahrain's government has crushed dissent and violently cracked down on protests in the past year, Amnesty International said on Thursday, and it accused Britain and the United States in particular of turning a blind eye to its abuses.
Amnesty said in a report on Thursday that it had documented how the Bahraini government, from June 2016 to June 2017, arrested, tortured, threatened or banned from travel at least 169 activists and opponents or their relatives.
"Despite repeated claims ... to the contrary, Bahrain has been steadily backtracking on the promises of reform it made following its heavy-handed response to the uprising in 2011," Amnesty said.
Bahraini authorities could not immediately be reached for comment. Bahrain has repeatedly denied systematic rights abuses.
Entitled "No one can protect you: Bahrain's year of crushing dissent," the report said that at least six people were killed, including a child, in the crackdowns.
The report also accused Western governments, notably the United States and Britain of remaining silent.
The two countries have a particularly high level of influence in Bahrain, where the US Fifth Fleet is based and where Britain's Royal Navy has a major facility.
Amnesty said US President Donald Trump's policy has shifted from that of his predecessor, Barack Obama, who had publicly criticised the authorities of the tiny Gulf state.
"In March 2017, President Trump told Bahrain's King Hamad 'there won't be strain with this administration': Bahrain appears to have interpreted this statement as a green light to pursue its repression," the report said.
Authorities in the tiny Sunni-ruled Gulf kingdom launched a crackdown after an Arab Spring-inspired movement of largely Shia protesters hit the streets in 2011 to demand an elected government.
The king this year approved a constitutional amendment allowing military courts to try citizens on charges linked to terrorism.
Bahrain has also stepped up a crackdown on critics, shutting down two main political groups, revoking the citizenship of the spiritual leader of the Shia Muslim community and jailing rights campaigners. It denounced attempts by previous US and UK governments to intervene in its campaign.
In July, a Bahraini court sentenced rights campaigner and prominent activist Nabeel Rajab to two years in jail for allegedly making "false or malicious" statements about Bahraini authorities. Rajab is facing another trial and risks a further 15 years in prison for tweeting.
"Using an array of tools of repression, including harassment, arbitrary detention and torture, the government of Bahrain has managed to crush a formerly thriving civil society," Philip Luther, Amnesty International's director for the Middle East and North Africa, said in a statement.
Amnesty said it had received reports of nine cases of government critics being tortured in detention, eight of them in May 2017 alone.
Bahrain has been a flashpoint since the island's ruling Sunni minority put down protests during the Arab uprisings in 2011.
The kingdom, most of whose population is Shia, says it faces a threat from neighbouring Iran.
It accuses Iran of radicalising and arming some members of its majority Shia population in an effort to bring about the downfall of the ruling Khalifa family.
Tehran denies any meddling in Bahrain.
The full report can be read here.