Quds Day (lit. 'Jerusalem Day'), officially known as International Quds Day (Persian: روز جهانی قدس, romanized: Ruz Jahâni Quds), is an annual pro-Palestinian event held on the last Friday of the Islamic holy month of Ramadan to express support for Palestinians and oppose Israel and Zionism. It takes its name from the Arabic name for Jerusalem: al-Quds.

The event was first held in 1979 in Iran, shortly after the Iranian Revolution. The day exists partly in opposition to Israel's Jerusalem Day, which has been celebrated by Israelis since May 1968 and was declared a national holiday by the Knesset in 1998. Today, rallies are held on Quds Day in various countries in the Muslim world, as well as in non-Muslim communities around the world, in protest against the Israeli occupation of East Jerusalem.

Critics of Quds Day have argued that it is antisemitic. In Iran, the day is marked by widespread speeches (some featuring Holocaust denial) and rallies that have been frequented by chants of "Death to Israel, Death to America", with crowds trampling and burning Israeli flags. Quds Day rallies have also featured demonstrations against other countries and causes.

An annual anti-Zionist day of protest was first suggested by Ebrahim Yazdi, the first foreign minister of the Islamic Republic of Iran, to Ruhollah Khomeini, the leader of the Iranian Revolution. At the time, its predominant context was related to deepening tensions between Israel and Lebanon. Khomeini adopted Yazdi's idea, and on August 7, 1979, he declared the last Friday of every Ramadan as "Quds Day", in which Muslims worldwide would unite in solidarity against Israel and in support of the Palestinians. Khomeini stated that the "liberation" of Jerusalem was a religious duty to all Muslims:

I invite Muslims all over the globe to consecrate the last Friday of the holy month of Ramadan as Al-Quds Day and to proclaim the international solidarity of Muslims in support of the legitimate rights of the Muslim people of Palestine. For many years, I have been notifying the Muslims of the danger posed by the usurper Israel which today has intensified its savage attacks against the Palestinian brothers and sisters, and which, in the south of Lebanon in particular, is continually bombing Palestinian homes in the hope of crushing the Palestinian struggle. I ask all the Muslims of the world and the Muslim governments to join together to sever the hand of this usurper and its supporters. I call on all the Muslims of the world to select as Al-Quds Day the last Friday in the holy month of Ramadan—which is itself a determining period and can also be the determiner of the Palestinian people's fate—and through a ceremony demonstrating the solidarity of Muslims worldwide, announce their support for the legitimate rights of the Muslim people. I ask God Almighty for the victory of the Muslims over the infidels.

— Ruhollah Khomeini, 1979

Senior clerics, including Ayatollah Naser Makarem Shirazi, have described participation in Quds Day as a form of religious worship (ebādat), intended to unite Muslims around the world.

There have been recorded incidents of violence on Quds Day, including 28 people killed and 326 wounded by bombs in 1985 during the Iran–Iraq War. Iran celebrates the event characteristically by putting on public display poster images of the city of Jerusalem, thematic speeches, art exhibitions reflecting the issue, and folkloric events. In Lebanon, Hezbollah marks the occasion by organizing a substantive military parade for the last week of each Ramadan. Since 1989, Jordan has observed the event by hosting academic conferences, whose venue from university to university varies each year. Arab societies generally pay the occasion lip service in order to make a show of solidarity with the cause of Palestinian aspirations for nationhood.