The First Surah, Surah Al-Alaq (Order And Arrangement Of The Quran).
It is authentically reported that the first verses (five ayats (1-5)) to be revealed to Holy Prophet Muhammad ﷺ were the initial verses of Surah al Alaq (the 96th Chapter of the Holy Quran).
Read, in the name of your Lord who has created! He has created man from a clinging clot. Read! For your Lord is the Most Gracious, who has taught by the pen, has taught man what he has known not! [Sûrat Al-ʿAlaq, 96:1-5]
According to Sahih al-Bukhari, Sayyidah A'ishah رضي الله عنها narrates that the very first revelations came to the Holy Prophet Muhammad ﷺ through true dreams.