What body has the power to ratify treaties?

The President has the power to make treaties, but they are not valid until 2/3 of the Senate ratifies them.

http://en.wikipedia.org/wiki/President_of_the_United_States#Powers

thank you so much. im trying to do this constitution packet and im struggling big time. im going to keep posting questions if you would like to help. i would GREATLY appreciate it.

You're welcome! I'm here to help with any questions you have. Feel free to continue posting your questions and I'll do my best to assist you. Just let me know what you need help with, and I'll provide you with explanations and resources to support your understanding.