A standing rib roast, also known as prime rib, is a cut of beef from the primal rib, one of the nine primal cuts of beef. While the entire rib section comprises ribs six through 12, a standing rib roast may contain anywhere from two to seven ribs.
It is most often roasted "standing" on the rib bones so that the meat does not touch the pan. An alternative cut removes the top end of the ribs for easier carving.
Rib-eye steaks are cut from a standing rib, boned with most of the fat and lesser muscles removed.
While often referred to as "prime rib", the USDA does not require the cut to be derived from USDA Prime grade beef.