The Largest Lake in the World

World's Largest Lake (by surface area):

 Caspian Sea

The salty Caspian Sea has the greatest surface area of any lake at 143,200 square miles (370,886 square kilometers). Lake Superior, on the United States/Canada border, is the named freshwater lake with the greatest surface area at 31,700 square miles (82,103 square kilometers). 

World's Largest Lake (by volume):

Lake Baikal

Lake Baikal is the world's largest freshwater lake in terms of volume. It contains about 5,521 cubic miles of water (23,013 cubic kilometers), or approximately 20% of Earth's fresh surface water. This is a volume of water approximately equivalent to all five of the North American Great Lakes combined.

While Lake Baikal is extremely deep, its surface area is only about 12,248 square miles (31,722 square kilometers), putting it in seventh place worldwide in terms of surface area.

Sources : Google Images & Wikipedia