A dissident is a person who actively challenges an established political or religious system, doctrine, belief, policy, or institution. In a religious context, the word has been used since 18th century, and in the political sense since 1940, coinciding with the rise of totalitarian systems, especially the Soviet Union, Nazi Germany, and Saudi Arabia. In the Western World there are historical examples of people who have been considered and have considered themselves dissidents, such as the Dutch philosopher Baruch Spinoza. In totalitarian regimes, dissidents are often incarcerated without explicit political accusations, or due to infringements of the very same laws they were disputing, or because they are supporting progressive rights such as the free speech right.
The term dissident was used in the Eastern bloc, particularly in the Soviet Union, in the period following Joseph Stalin's death until the fall of communism. It was attached to citizens who criticized the practices or the authority of the Communist Party. Writers for the non-censored, non-conformist samizdat literature were criticized in the official newspapers. Soon, many of those who were dissatisfied with the Soviet Bloc began to self-identify as dissidents. This radically changed the meaning of the term: instead of being used in reference to an individual who opposes society, it came to refer to an individual whose non-conformism was perceived to be for the good of a society. In Hungary, the word disszidens was used in contemporary language for a person who had left for the West without permission (i.e. a defector), by illegally crossing the border or travelling abroad with a passport, but not returning and (sometimes) applying for asylum abroad. Such persons' citizenship was usually revoked, and their left behind property (if there was any to their name) would revert to the state.
Main article: Soviet dissidents
Soviet dissidents were people who disagreed with certain features in the embodiment of Soviet ideology and who were willing to speak out against them. The term dissident was used in the Soviet Union in the period following Joseph Stalin's death until the fall of communism. It was used to refer to small groups of marginalized intellectuals whose modest challenges to the Soviet regime met protection and encouragement from correspondents. Following the etymology of the term, a dissident is considered to "sit apart" from the regime. As dissenters began self-identifying as dissidents, the term came to refer to an individual whose non-conformism was perceived to be for the good of a society.
Political opposition in the USSR was barely visible and, with rare exceptions, of little consequence. Instead, an important element of dissident activity in the Soviet Union was informing society (both inside the Soviet Union and in foreign countries) about violation of laws and human rights. Over time, the dissident movement created vivid awareness of Soviet Communist abuses.
Soviet dissidents who criticized the state faced possible legal sanctions under the Soviet Criminal Code and faced the choice of exile, the mental hospital, or the labor camp. Anti-Soviet political behavior, in particular, being outspoken in opposition to the authorities, demonstrating for reform, writing books were defined in some persons as being simultaneously a criminal act (e.g., violation of Articles 70 or 190-1), a symptom (e.g., "delusion of reformism"), and a diagnosis (e.g., "sluggish schizophrenia").
See also: Dissident republican
The term dissident has become the primary term to describe Irish republicans who politically continue to oppose Good Friday Agreement of 1998 and reject the outcome of the referendums on it. These political parties also have paramilitary wings which espouse violent methods to achieve a United Ireland.
Irish republican dissident groups include the Irish Republican Socialist Party (founded in 1974 – its currently-inactive paramilitary wing is the Irish National Liberation Army), Republican Sinn Féin (founded in 1986 – its paramilitary wing is the Continuity IRA), and the 32 County Sovereignty Movement (founded in 1997 – its paramilitary wing is the Real IRA). In 2006 the Óglaigh na hÉireann emerged, which is a splinter group of the Continuity IRA.
Dissidents and activists were among the earliest adopters of encrypted communications technology such as Tor and the dark web, turning to the technology as ways to resist authoritarian regimes, avoid censorship and control and protect privacy.
Tor was widely used by protestors on Mubarak regime in Egypt in 2011. Tor allowed dissidents to communicate anonymously and securely, while sharing sensitive information. Also, Syrian rebels widely used Tor in order to share with the world all of the horrors that they witnessed in their country. Moreover, government dissidents in Lebanon, Mauritania, as well as Arab Spring nations widely used Tor in order to stay safe while exchanging their ideas and agendas.
Jamal Khashoggi was a Saudi-American dissident and journalist. He was murdered inside a Turkish embassy by Saudi Arabian authorities.
Various other Human rights activists from Saudi Arabia have been either silenced or punished. This also happens if the individual is outside the country. Deportation is used if they are not Saudis.
The Fact Finding Panel (FFP), an independent jury of British parliamentary members and international attorneys, was mandated to review the detention state of former Crown Prince of Saudi Arabia Mohammed bin Nayef and Prince Ahmed Bin Abdulaziz Al Saud. In the mid of December 2020, the panel published a report stating its findings, which claimed that the detention of the political prisoners collectively in the Kingdom of Saudi Arabia has been violating the country's international legal obligation by holding the detainees without charge and not allowing them a chance to challenge their imprisonment. The imprisonment has also risked the safety of the detainees by posing fatal risks to their health conditions by keeping them behind the bars, without providing proper medical aid amid the ongoing COVID-19 pandemic.
Another monarchy of the Middle East, Bahrain is known for curbing the rights of peaceful critics, including political activists and human rights defenders. A report released by Amnesty International in 2017 revealed that the country opted for several repressive tactics, including arbitrary detention, torture and harassment, between June 2016 and June 2017 to crush the dissidents. Several human rights organizations and international leaders have consistently denounced Bahrain's poor human rights records. 
The Human Rights Watch World Report 2021 also highlighted that Bahrain continued its repressive actions against the dissidents, including acts against online activities, peaceful critics and opposition activists. Besides, in January 2021, forty cross-party MPs of the UK wrote a letter to the vice-chancellor of an educational institution, the University of Huddersfield, stating that it was at risk of “indirect implication in human rights abuse”. The university was running a master’s course, MSc in security science, for the officers of Bahrain’s Royal Academy of Policing, the building which was also being used for torturing dissidents.
In April 2021, the European Parliament adopted a resolution on Bahrain, especially concerning the cases of detained dissidents Nabeel Rajab, Abdulhadi al-Khawaja and Ibrahim Sharif. With 48 votes in favor, the MEPs condemned Bahrain for its human rights violations and called for an immediate release of all the political activists, prisoners in conscience, human rights defenders, journalists and peaceful protesters. The European Parliament also demanded the Bahraini government to take all necessary measures to respect the laws and make sure that its actions remain in full compliance with the international standards of human rights.