Zakat (or Zakāh) is one of the Five Pillars of Islam. Zakat is the Arabic word for "giving to charity" or "giving to the needy". Zakat is a form of almsgiving, often collected by the Muslim Ummah. It is considered in Islam a religious obligation, and by Quranic ranking, is next after prayer (salat) in importance. Eight heads of zakat are mentioned in the Quran.

As one of the Five Pillars of Islam, zakat is a religious duty for all Muslims who meet the necessary criteria of wealth to help the needy. It is a mandatory charitable contribution, often considered to be a tax. The payment and disputes on zakat have played a major role in the history of Islam, notably during the Ridda wars.^{[page needed]}

Zakat on wealth is based on the value of all of one's possessions. It is customarily 2.5% (or 1⁄40) of a Muslim's total savings and wealth above a minimum amount known as nisab each lunar year, but Islamic scholars differ on how much nisab is and other aspects of zakat. According to Islamic doctrine, the collected amount should be paid to the poor and the needy, Zakat collectors, orphans, widows, those to be freed from slavery, the aged who cannot work to feed themselves, those in debt, in the cause of God and to benefit the stranded traveller.

Today, in most Muslim-majority countries, zakat contributions are voluntary, while in Libya, Malaysia, Pakistan, Saudi Arabia, Sudan and Yemen, zakat is mandated and collected by the state (as of 2015).

Shias, unlike Sunnis, have traditionally regarded zakat as a private action, and they give zakat to imam-sponsored rather than state-sponsored collectors, but it is also obligatory for them.

The word Zakat comes from Arabic root z-k-w (ز ك و), meaning to purify. Zakat is considered a way to purify one's income and wealth from sometimes worldly, impure ways of acquisition. According to Sachiko Murata and William Chittick, "Just as ablutions purify the body and salat purifies the soul (in Islam), so zakat purifies possessions and makes them pleasing to God."

The Quran discusses charity in many verses, some of which relate to zakat. The word zakat, with the meaning used in Islam now, is found, for example, in suras: 7:156, 9:60, 19:31, 19:55, 21:73, 23:4, 27:3, 30:39, 31:4, and 41:7. Zakat is found in the early Medinan suras and described as obligatory for Muslims. It is given for the sake of salvation. Muslims believe those who give zakat can expect reward from God in the afterlife, while neglecting to give zakat can result in damnation. Zakat is considered part of the covenant between God and a Muslim.

Verse 2:177 (the Clear Qur'an translation) sums up the Quranic view of charity and almsgiving (another name for zakat is the poor due):