The Gayatri Mantra is a Sanskrit mantra that has been chanted for thousands of years. It was written down during the Vedic period (1500-500 BCE) and is considered to be one of the oldest known and most powerful mantras. It is said to contain all the knowledge of the universe.
The Gayatri Mantra Lyrics:
Om bhuh, bhuvah, swaha
Tat savitur varenyam
Bhargo devasya dhimahi
Dhiyo yo nah prachodayat

The meaning of the Gayatri Mantra
A general translation of the mantra is:

O Divine mother, may your pure divine light illuminate all realms (physical, mental and spiritual) of our being. Please expel any darkness from our hearts and bestow upon us the true knowledge.