Cape Cod Bay wani babban ruwa ne da ke bakin tekun Massachusetts, Amurka, zuwa gabas da tsibirin Cape Cod. Mashigar ruwa ce ta Tekun Atlantika kuma tana da kusan mil 604 murabba'in yanki. Sunan bakin tekun bayan tsibirin Cape Cod, wanda ya zama gefen gabas, kuma "Bay" yana nufin babban ruwan gishiri wanda ƙasa ke rufe. An san yankin da tarin tarihin teku, da yawan rayuwar ruwa, da kyan gani, kuma wuri ne da ya shahara wajen gudanar da ayyukan nishadi kamar su kamun kifi, kwale-kwale, da ninkaya.