It's the most iconic prayer in Christendom; also called, "The Lord's Prayer." I could identify it even when I was an atheist even though I didn't know all the words. It's a good first one to learn and the most commonly occurring. If you're around Catholics, it won't be long before a group of people is reciting this one in unison. So just learn it.
Our Father, who art in heaven, hallowed be thy name; thy kingdom come; thy will be done on earth as it is in heaven. Give us this day our daily bread, and forgive us our trespasses, as we forgive those who trespass against us; and lead us not into temptation, but deliver us from evil. Amen.
Pater noster, qui es in caelis, sanctificetur nomen tuum. Adveniat regnum tuum. Fiat voluntas tua, sicut in caelo et in terra. Panem nostrum quotidianum da nobis hodie, et dimitte nobis debita nostra, sicut et nos dimittimus debitoribus nostris. Et ne nos inducas in tentationem, sed libera nos a malo. Amen.