The naqus (Arabic: ناقوس, romanized: nāqūs; Syriac: ܢܩܘܫܐ) is a percussion musical instrument, and under that name there are a set of traditions associated with Islamic-Christian relations. It can either be a bell or a wooden plank; in the latter form, it is similar to the semantron.

The Arabic word nāqūs goes back to the Syriac naqosha (from naqash, "to strike") and reached the Aethiosemitic languages with the meaning "gong", "handbell". The show the two meanings of nagus...a billet of wood struck, and a bell or hand-bell.

The instrument called a naqus is also referred to in the Bahá'í document Lawh-i-Naqus, "Tablet of the Bell". This "indicates a pierced wooden clapper-board which had a gong or bell-like function in making a noise when hit with a stick."

According to Islamic tradition, the companions of Muhammad were unsure of what the sign for the daily prayers (salāt) should be. Mohammad therefore decided between a fire, a bell, a Jewish horn (shofar) and the nāqūs for the muezzin's call to prayer (adhān). Apparently, in the early days of Fustat, the Muslims struck the nāqūs as an early-morning call to prayer. The sound of the nāqūs as a call to prayer was heard along with the crowing of the cocks.

The name naqus was used among Christians too, who used the nāqūs since pre-Islamic times. Clattering wood (nāqūs) was mentioned by the poet Labīd (around 560 —661), who saw them in villages on the coast southwest of Qatar on the Arabian Peninsula. Archaeological excavations at a pre-Islamic Nestorian monastery on an island west of Abu Dhabi suggest that the church had an upper floor with a steeple, which probably contained a wooden nāqūs instead of a bell.

In general, the nāqūs has often been at the center of cultural tensions between Christians in Arab areas. After Caliph Al-Walid I had the Byzantine cathedral of Damascus converted into the Umayyad Mosque around 705, al-Masʿūdī reported an incident that caused irritation. At the moment when the caliph mounted the minbar in the mosque to address the believers, a nāqus was heard. The proximity between the church and the mosque often seems to have caused noise pollution.

The Islamic scholar Abu Yusuf (729/731-798) mentioned in his Kitāb al-Ḫarāğ (“Book on Property Tax”) the obligations that Christians had to observe under Islamic rule. This included not striking the nāqūs before or during Islamic prayer times. Elsewhere it is stated that the nāqūs should only be played softly or only within the church. These restrictions are also confirmed by the orthodox side, such as the patriarch Michael the Syrian (1126-1199) and the scholar Gregorius Bar-Hebraeus (c. 1225-1286). The naqus hitting loudly in public was considered a violation of the law. In return, Christian dignitaries were sometimes given permission to beat drums and play trumpets or other musical instruments at special religious ceremonies. The cauldron drum naqqara and long trumpets (buk) have been used to honor rulers since ancient times.

The Jewish scholar Daniel al-Kumisi († 946) wrote that the use of the nāqūs was characteristic of the Christians of Jerusalem around 900. A mid-11th-century account of a town believed to be in Palestine mentions that the Christians ignored the existing laws and built a church higher than the local mosque. The church was then demolished, and the loud beating of the nāqūs also disturbed the Muslims.