Africa is the continent containing both the Equator and the Prime Meridian.
The Equator crosses Africa from the Atlantic coast through countries including Gabon, the Republic of the Congo, the Democratic Republic of the Congo, Uganda, Kenya, and Somalia. The Prime Meridian, defined as 0 degrees longitude, crosses western Africa through Ghana, Burkina Faso, Togo, and Algeria.
Because the two lines intersect near the Gulf of Guinea, Africa occupies all four hemispheres: northern, southern, eastern, and western. This is a geographic distinction rather than a political one, since hemisphere boundaries are defined by coordinate lines.
South America contains the Equator and lies in both eastern and western hemispheres, but the Prime Meridian does not cross it. Europe includes the Prime Meridian, yet the Equator is far to its south. That combination makes Africa the only continent crossed by both lines.