Ordinance XX (Urdu: آرڈیننس 20) is a legal ordinance of the Government of Pakistan that was promulgated under the regime of General Muhammad Zia-ul-Haq on 26 April 1984 and is meant to prohibit the practice of Islam and the usage of Islamic terms and titles for the Ahmadiyya Muslim Community. The ordinance bars Ahmadi Muslims, who are deemed Non-Muslims under the Pakistani constitution, from publicly practising the Islamic faith and also disallows them from using any Islamic texts for praying purposes. It is in addition to – but separate from – the 1974 Second Amendment to the Constitution of Pakistan. While the Second Amendment declared that Ahmadis are non-Muslims, the Ordinance prohibits Ahmadis from identifying themselves as Muslims.
The ordinance also debars Ahmadis from the use of any honorific titles and modes of address deemed specific to the Islamic community such as the greeting "As-salamu alaykum" (peace be upon you), reciting the Six Kalimas or the shahada (declaring belief in the oneness of God and the prophethood of Muhammad) etc., from building mosques and calling the Adhan (call to prayer), from undertaking Muslim modes of worship, from worshipping in non-Ahmadi mosques or public prayer rooms, and from making any citations from the Quran and Muhammad's hadith. Punishment for anyone convicted of doing any of the above is imprisonment of up to three years and a fine. Ahmadis, who self-identify as Muslims and practice Islam, claim that the Ordinance criminalises their everyday life. expressing the Kalima (Muslim creed) and greeting with peace in the Muslim way is a criminal offence for Ahmadis in Pakistan.