What is located on your right side underneath the top of your ribcage?

Lung: If i understand your question, the rib cage contains your right lung in that area you describe.

It is not what is : There it is why are you asking that question? I am not an internist or general surgeon but pain there can be referred from elsewhere. Can be from so much. Not to worry but liver and gallbladder, intestines, lung, kidney, heart and large arteries, gynecological issues ...All can cause what is known as right upper quadrant pain. So if it is pain, call pcp andsay where, how often, after eating, etc e.