As-salamu alaykum (Arabic: ٱلسَّلَامُ عَلَيْكُمْ, as-salāmu ʿalaykum, Arabic: [as.sa.laː.mu ʕa.laj.kum] (listen)), also written salamun alaykum and typically rendered in English as salam alaykum, is a greeting in Arabic that means 'Peace be upon you'. The salām (سَلَام, meaning 'peace') has become a religious salutation for Muslims worldwide when greeting each other, though its use as a greeting pre-dates Islam, and is also common among Arabic speakers of other religions (such as Arab Christians and Mizrahi Jews).

In colloquial speech, often only the first part of the phrase (so: salām, 'peace') is used to greet a person. The typical response to the greeting is wa ʿalaykumu s-salām (وَعَلَيْكُمُ ٱلسَّلَامُ, Arabic: [wa ʔa.laj.kum mus.sa.laːm] (listen), 'and peace be upon you'). The complete phrase is as-salāmu ʿalaykum wa-raḥmatu -llāhi wa-barakātuh^ū (ٱلسَّلَامُ عَلَيْكُمْ وَرَحْمَةُ ٱللَّٰهِ وَبَرَكَاتُهُ, [as.sa.laː.mu ʕa.laj.kum wa.raħ.ma.tu‿ɫ.ɫaː.hi wa.ba.ra.kaː.tu.huː]), 'Peace be upon you, as well as the mercy of God and his blessings'.

This greeting in its abbreviated form, salām (سَلَام), has come to be used as the general salutation in other languages as well. Among Christians, during Mass or other liturgical services, the priest or pastor and the congregation often use the salutation, "peace be with you", sometimes replying, "and also with you".

Cognate Semitic language parallels include the Aramaic/Classical Syriac šlāmā ʿalḵōn (ܫܠܵܡܵܐ ܥܲܠܟ݂ܘܿܢ), and the Hebrew shalom aleichem (שָׁלוֹם עֲלֵיכֶם shālôm ʻalêḵem).