Alhamdulillah (, ) is an Arabic phrase meaning "praise be to God", sometimes translated as "thank God" or "thanks be to the Lord". This phrase is called Tahmid (). A longer variant of the phrase is al-ḥamdu l-illāhi rabbi l-ʿālamīn (ٱلْحَمْدُ لِلَّٰهِ رَبِّ ٱلْعَالَمِينَ), meaning "all praise is due to God, Lord of all the worlds", the first verse of Surah Al-Fatiha, the opening chapter of the Quran.
The phrase is frequently used by of every background due to its centrality in the texts of the Quran and Hadith, the words of the Islamic prophet Muhammad. Its meaning and in-depth explanation have been the subject of much exegesis. It is also commonly used by non-Muslim speakers of the Arabic language.
A similar variation used in Christianity is the phrase "Hallelujah".
The phrase is first found in the first verse of the first sura of the Qur'an (Al-Fatiha). So frequently do Muslims and Arabic-speaking Arab Jews and Arab Christians invoke this phrase that the Semitic root verb hamdala (), "to say al-ḥamdu li-llāh" was coined, and the derived noun ḥamdala is used as a name for this phrase.
The triconsonantal root Ḥ-M-D (), meaning "praise", can also be found in the names Muhammad, Mahmud, Hamid and Ahmad, among others.