The Gayatri Mantra- (most well known Sanskrit mantras)

Om bhur bhuvah svah
tat savitur varenyam
bhargo devasya dhimahi
dhiyo yonah prachodayat

It basically translates into something like:

We meditate on the glory of the Creator;
Who has created the Universe;
Who is worthy of Worship;
Who is the embodiment of Knowledge and Light;
Who is the remover of all Sin and Ignorance;
May He enlighten our Intellect.