The Equator, that solid imaginary horizontal line at 0º degrees latitude at the center of the earth, divides the earth into the Northern and Southern Hemispheres.

The vertical imaginary line called the Prime Meridian, at 0º degrees longitude, and its twin line of longitude, opposite the Prime Meridian at 180º longitude, divides the earth into the Eastern and Western Hemispheres.

Therefore all countries north of the Equator are in the Northern Hemisphere, while all countries south of the Equator are in the Southern Hemisphere.

Generally speaking the Eastern Hemisphere consists of Europe, Africa, Asia, and Australia while the Western Hemisphere includes North and South America. Some countries, based on that straight line division, are parts of two hemispheres.