Hamas is a Palestinian Islamic fundamentalist group, classified by the US State Department as a terrorist organization. Their stated goal is to overthrow the State of Israel, the West Bank and Gaza, and Kingdom of Jordan, and replace them with an Islamic theocracy.
The United States Department of State has presented the following information on Hamas, from the Office of Counterterrorism:
Description: Formed in late 1987 as an outgrowth of the Palestinian branch of the Muslim Brotherhood. Various Hamas elements have used both political and violent means, including terrorism, to pursue the goal of establishing an Islamic Palestinian state in place of Israel. Loosely structured, with some elements working clandestinely and others working openly through mosques and social service institutions to recruit members, raise money, organize activities, and distribute propaganda. Hamas's strength is concentrated in the Gaza Strip and a few areas of the West Bank. Also has engaged in peaceful political activity, such as running candidates in West Bank Chamber of Commerce elections. Activities: Hamas activists, especially those in the Izz el-Din al-Qassam Brigades, have conducted many attacks--including large-scale suicide bombings--against Israeli civilian and military targets, suspected Palestinian collaborators, and Fatah rivals.
Unknown number of hardcore members; tens of thousands of supporters and sympathizers. Receives funding from Palestinian expatriates, Iran, and private benefactors in Saudi Arabia and other moderate Arab states. Some fundraising and propaganda activity take place in Western Europe and North America.
At the time of this writing, there is a close relationship between the leadership of the PLO and Hamas.