T-bone steak is the traditional name in United States. Outside that tradition, butchers carry comparable beef cuts under different names — sometimes the same anatomical piece, sometimes a close cousin. The alternatives below are grouped by country so you can match what your local butcher actually carries.
Both contain strip and tenderloin separated by a T-bone, but the porterhouse is cut further back and has a substantially larger tenderloin portion — the USDA requires at least 1.25 inches of tenderloin for a porterhouse.
Both are dramatic bone-in steaks, but the T-bone comes from the short loin and includes both strip and tenderloin