Dua for Forgiveness in Ramadan
اللَّهُمَّ أَنْتَ رَبِّي لَا إِلَهَ إِلَّا أَنْتَ خَلَقْتَنِي وَأَنَا عَبْدُكَ
Allahumma anta Rabbi la ilaha illa anta khalaqtani wa ana ‘abduk
“O Allah, You are my Lord; there is no god but You. You created me and I am Your servant.”
Sahih al-Bukhari 6306 (the opening of Sayyid al-Istighfar).
Why Ramadan
“Whoever fasts Ramadan out of faith and seeking reward will have his previous sins forgiven” (Sahih al-Bukhari 38). Pair istighfar with leaving the sin and restoring anyone’s rights you have harmed.
Transliteration is a guide only; recite from the Arabic where you can. References are given so you can verify each wording.