Hamas is a Palestinian nationalist Sunni Islamist organization, founded during the First Intifada in 1987. While Hamas played a minor role in the Intifada, it successfully used the Intifada to grow and position itself as an alternative to the secular, left-wing Palestinian Liberation Organisation following the end of the Intifada and the start of the Oslo Accords peace process.

On 9 December 1987, an Israeli truck driver collided with and killed four Palestinians in the Jabalia refugee camp. The incident sparked the largest wave of Palestinian unrest since the Israeli occupation began in 1967: the First Intifada. During the early stages, the Intifada was largely characterised by a non-violent campaign led by a decentralised, grassroots leadership, with actions including labour strikes, tax strikes, boycotts of Israeli goods, boycotts of Israeli institutions, demonstrations, the establishment of underground classrooms and cooperatives, raisings of the banned Palestinian flag, and civil disobedience. The Israeli government responded to the breakout of the Intifada with a harsh crackdown, however, and the Intifada grew more violent during its last stages, including Palestinian internal political violence against rumoured collaborators. By the end of the Intifada, over a thousand Palestinians had been killed and over a hundred thousand injured by Israeli forces, with around two hundred Israelis having been killed by Palestinians. The First Intifada would come to an end with several high-profile peace negotiations, including the Madrid Conference of 1991 and the 1993 Oslo Accords.

During the 1970s and early 1980s, the Muslim Brotherhood in the Gaza Strip, led by Ahmed Yassin and his Mujama al-Islamiya charity, grew significantly, building a network of mosques, schools, clubs, and offering social services. Yassin's network received support from the Israeli government during this period, who believed that it could serve as an alternative within Palestinian society that would undermine the influence of the secular, left-wing PLO. As the 1980s continued, however, Yassin's network would begin to turn towards the idea of re-organising itself into a paramilitary group capable of participating in the Israeli-Palestinian Conflict, in part due to pressure from the founding of the Palestinian Islamic Jihad, formed in 1981 from extremist members who split from the Brotherhood. Yassin was arrested and jailed by the Israeli military for stockpiling weapons and calling for Israel to be annihilated. Yassin was subequently released in 1985, as part of the Jibril Agreement.

On 14 December 1987, several days after the breakout of the First Intifada, Yassin and several other prominent of the Brotherhood network in Gaza released a leaflet announcing the formation of a new movement: Ḥarakat al-Muqāwamah al-ʾIslāmiyyah, the Islamic Resistance Movement, abbreviated as Hamas, the Arabic word for zeal. According to Jean-Pierre Filiu of Sciences Po, the outbreak of the Intifada was "as much a surprise to the Muslim Brotherhood as to the PLO. The Islamist leadership was tempted to keep a low profile, and it was ultimately Shaykh Yasin who imposed on his divided followers his decision to participate in the uprising against Israel." According to Palestinian academic Khaled Hroub, the factors that led to the founding of Hamas with the breakout of the First Intifada included: internal debates within the Muslim Brotherhood over its stance towards the Israeli occupation, with parts of the organisation calling for the priority to be confronting Israel and other parts calling for the priority to be Islamising Palestinian society; the growing resentment against the occupation and poverty among the population of the Gaza Strip; as well as rivalry with the fast-growing and more militant Palestinian Islamic Jihad.

In August 1988, Hamas formulated its founding charter, containing 36 short articles. The charter portrayed the Israeli-Palestinian conflict as a war between Muslims and Jews, and containing a significant amount of genocidal and antisemitic language, including references to the forged The Protocols of the Elders of Zion. In its charter, Hamas claimed that "the land of Palestine is an Islamic trust left to the generations of Moslems until the day of resurrection" and that "the solution to the Palestinian problem will only take place by holy war," rejecting all peace initiatives. The charter also claimed that "Israel will exist and will continue to exist until Islam will obliterate it" and that "The Day of Judgment will not come about until Muslims fight Jews and kill them."

Following the launch of its charter, Hamas began agitating to take greater control over the Intifada and to replace the PLO-affiliated Unified National Leadership of the Uprising. In a September 1988 article, Ian Black of British newspaper The Guardian wrote that Hamas represented "an increasingly powerful opposition to those who seek to translate the sacrifices of the uprising into concrete political gains," opposing any concessions to Israel, and that "as the PLO has faced the challenge of matching months of sustained unrest with politically imaginative ideas, Hamas has become firmer in its views."

In mid-November 1988, the PLO's Palestinian National Council was convened in Algiers, Algeria, to draft and issue the Palestinian Declaration of Independence, establishing the State of Palestine as a government-in-exile and calling for peace negotiations based on the 1967 United Nations Security Council Resolution 242. The declaration was met with scepticism by the Israeli government, who also ordered a lockdown on the Palestinian Territories over the duration of the PNC conference, and received a muted response among Palestinians. Hamas would be one of the most prominent groups to speak out against the declaration, on the basis that it accepted the 1947 Partition of Palestine, describing it as a surrender. Later that month, as the first anniversary of the breakout of the Intifada approached and frustrations were growing among the Palestinian population over the continuing harsh Israeli crackdown, when the UNLU called for the date of the annual day of protests against the partition to be changed as a result of the declaration, Hamas called for protests to be held on the usual date in defiance of the UNLU. The call was largely followed and received support from the PLO hardliners, the Popular Front for the Liberation of Palestine (PFLP).

According to Gil Sedan and Hugh Orgel of the Jewish Telegraphic Agency, during the first year and a half of the First Intifada, "the official attitude toward Hamas and its leadership has been more or less tolerant. Senior figures in the defence establishment have stated privately that two considerations supported the policy of encouraging Hamas' influence among the Palestinians. One was the notion that granting a firm public standing to the Islamic elements, even religious and political extremists, would offset the influence of violent groups, such as the Islamic Jihad. The other consideration was to strengthen the hand of PLO opponents within the Palestinian population." John Kifner of The New York Times wrote in September 1988 that "Israeli authorities have taken no direct action against Hamas despite repeated crackdowns and roundups" on UNLU and PLO factions, additionally quoting an anonymous Western diplomat as saying that "It certainly is remarkable with all these arrests, that someone like Sheik Ahmed Yassin, who just goes on saying the most awful things about Jews, isn't touched."

In early 1989, Hamas would perpetrate its first attack, posing as ultra-orthodox Jews to abduct and kill Israeli soldier Sergeant Avi Sasportas in February, and then Corporal Ilan Saadoun in early May. Following the killing of Sasportas and Saadon, the Israeli government began to perceive Hamas as a more serious threat, carrying out a mass arrest of over two hundred Hamas members, including Yassin, in late May 1989. In June 1989, the Israeli government formally designated Hamas as a terrorist organisation.

According to Alon Burstein of the Hebrew University of Jerusalem, Hamas presented itself as "the vanguard of a new Palestinian nationalism, expressing its identity through religion and calling for armed resistance against Israel and its replacement with an Islamic-Palestinian entity." According to Hani Awad of the Arab Center for Research and Policy Studies, the First Intifada saw "the newfound division of the political field between two major ideological forces whose understanding of the conflict with Israel was based on very different sets of principles," the first being the PLO with a veteran core and a statist nationalist ideology, and the second being Hamas, with a more inexperienced core and a ideology based on religious conflict. Awad further wrote that Hamas also presented a new national narrative during the Intifada, presenting Palestinian history through religious terms, particularly in contrast to the Israeli establishment's presentation of its own national narrative in Jewish terms.

In a 1991 article in The New York Times, Sabra Chartrand stated that there had been a significant increase in women wearing hijabs since the start of the First Intifada, particularly in the Gaza Strip, with many Palestinians having "adopted Islam and its rituals as a focus for the Palestinian cause, a source of ethnic pride and an alternative to the failures of secular political movements" even as "people close to events in Gaza say Palestinians here have not become more religious."

The outbreak of the First Intifada was largely spontaneous, and the uprising would be led by the grassroots organisations affiliated with the PLO, such as labour unions, student councils, and women's committees, who organised themselves together in the form of the Unified National Leadership of the Uprising. The central leadership of the PLO, who had mostly been exiled, imprisoned, or killed by 1987, played a relatively minor role in coordinating the Intifada. However, the PLO leadership regularly attempted to assert authority over the UNLU, largely succeeding by the later stages of the uprising. In this context, Hamas emerged as group that was entirely unaffiliated to the PLO, operating independently of the UNLU and often in opposition to the UNLU.

According to Khalid Farraj, a prominent Birzeit University student organiser of the Intifada, divisons grew significantly between Palestinian nationalist factions during the later stages of the Intifada, and "primary among the factors that deepened the rift was the meteoric rise of local Islamist movements, and particularly Hamas, which was staunchly opposed to the political process and committed to the armed struggle. The movement made huge inroads among the population during the intifada, and Hamas activists followed the directives of their own leadership — which were issued monthly — rather than abiding by UNLU directives."

According to Jean-Pierre Filiu of Sciences Po, "the relationship within the PLO between the leadership — exiled first in Jordan, then in Lebanon, and finally in Tunis — and the nationalists in the Gaza Strip (and to a lesser extent the West Bank) [has] been a complicated one. By contrast, because the Muslim Brotherhood of Gaza had hunkered down and consolidated its entrenchment in the Strip during the first two decades of the Israeli occupation, this tension between the 'outside' and the 'inside' has not been an issue for them." According to Francesco Saverio Leopardi of the University of Edinburgh, "the emergence of the Islamist camp represented a challenging development for the whole PLO since, for the first time, a genuinely Palestinian movement outside its framework gained increased popularity and legitimacy among the population."

During the First Intifada, Hamas routinely published leaflets describing its ideology and calling for Palestinians to take actions against Israel including strikes and demonstrations, often in contradiction to the UNLU's calls for action. In a 2017 study, Alon Burstein of the Hebrew University of Jerusalem found that Hamas leaflets during the First Intifada made more use of references to historical figures than Unified National Leadership of the Uprising leaflets, were more consistent who they identified as enemies and about their long-term vision for Palestine (particularly as the PLO shifted towards peace negotiations), and were "far more silent in the face of repression, with the only aspect accentuated as a result of repressive acts being the group's unique brand of religious-nationalism which Hamas framed as the collective's identity."

Hamas also used violence against Israelis. According to Kali Robinson of the Council on Foreign Relations, "Hamas's purpose was to engage in violence against Israelis as a means of restoring Palestinian backing for the Brotherhood, which was losing political support to Palestinian Islamic Jihad, a Gaza-based, Iran-sponsored organization that had begun pursuing terrorist operations against Israel." However, Hamas largely had yet to formulate a coherent military strategy.

When Egyptian President Hosni Mubarak proposed a 10-point peace initiative based on elections in September 1989, to which Arafat had signalled potential agreement, Hamas came out in opposition. In its 47th leaflet, it accused Mubarak and other Arab states of "working on American orders to tame the Palestinian people."

Hamas subsequently opposed the 1993 Oslo Accords, and refused to take part in the newly-formed Palestinian Authority. According to Palestinian sociologist Jamil Hilal, Hamas "presented itself as the main opposition to the Oslo Accords and succeeded in becoming a major political (and armed) force with the failure of the Oslo Accords to lead to a sovereign Palestinian State with East Jerusalem as its capital."

Academic Mustafa Fetouri wrote that, while "Hamas did not play a significant role in the First Intifada compared to well-established other Palestinian movements," its rise during the Intifada allowed it to subsequently claim a reputation of being "the beacon of grassroots resistance" to the Israeli occupation. According to Francesco Saverio Leopardi of the University of Edinburgh, Hamas emerged during the Intifada as "the new radical opponents to the moderate Fatah's leadership within the wider Palestinian national movement, a role attributed historically to the PFLP."

Following the abduction and killing of Nissim Toledano in late 1992, the Israeli government would carry out a mass deportation of four hundred Hamas members across the Lebanese border. The deportation, intended to eliminate Hamas as a security threat, backfired, with Hamas's profile being significantly raised and with Hamas forging its first links with Hezbollah, who provided the group with training and equipement. The next year, Hamas would perpetrate the Mehola Junction bombing, the first suicide bombing in the Israeli-Palestinian conflict, inspired by Hezbollah. Hamas would continue to grow and perpetrate terror attacks through the 1990s, and would become the most prominent Palestinian faction in the Second Intifada, which would be significantly more violent and militarised than the First.