OK, yes it is in Panamá, but that isn't my question!
Does it run from the Pacific in the West to the Caribbean in the East?
Or does it run from the Pacific in the West to the Atlantic in the East?
I admit - that was a trick question!
It runs from the Pacific in the EAST to the Caribbean in the WEST!
You see, Panama is mostly a country that, is predominantly an East to West country, not a North to South country.
And the Canal starts in the Pacific in the (South) EAST beside Panama city, and runs to the Caribbean in the (North) WEST beside the city of Colon.
And as far as my trick question. Some sources say that the Caribbean SEA is part of the Atlantic OCEAN, others say that the Caribbean sea BORDERS the Atlantic Ocean. So to decide whether the Panama Canal ends in the North West in the Atlantic or the Caribbean … it would always be correct to say the WEST end of the canal ends in the Caribbean Sea, but you'll have to decide the definition of Atlantic before you can say whether the WEST end of the Canal ends also in the Atlantic.
But you can always say that the EAST end of the canal ends in the Pacific Ocean.
Curious side note: If you say the Atlantic and the Caribbean are separate … the line that divides them includes the DEEPEST part of the Atlantic Ocean, in the Milwaukee Deep in the 800km long Puerto Rico trench.