The dividing line between the northern and southern hemisphere is the equator.
As you can see, the equator cross three continents, South America, Africa, and Asia:
The dividing line between the eastern and western hemisphere is the prime meridian on one side of the globe and 180th meridian on the other side (typically referred to as the international date line.
As you can see, the prime meridian crosses three continents, Europe, Africa, and Antarctica:
The only continent that is crossed by both the equator and the prime meridian is Africa.
The exact point where the equator crosses the prime meridian (0°N/S and 0°E/W) is in the Gulf of Guinea, which lies off the coast of west Africa.
EDIT TO ADD (and thanks to Ben Fielding for pointing this out):
Kiribati is a sovereign, independent island nation in the south-central Pacific:
It lies at it lies at 1.87° N to 3.37° S latitude, and 157.36° W to 173.00° E longitude. As you can see on the map above, both the equator and antimeridian (180°W) cross it. The means that part of Kiribati is in the northern hemisphere and part is in the southern hemisphere, and part is in the eastern hemisphere and part is in the western hemisphere. While Kiribati has a total land area is only 313 square miles (811 square km), the total breadth of all the islands expands 2,400 miles (3,900 km),
Since Kiribati is considered part of Oceania, that means Oceania is a second continent that lies in all four hemispheres.