Algeria is larger by total area than Saudi Arabia and Mexico.
Algeria covers about 2.38 million square kilometres, compared with roughly 2.15 million for Saudi Arabia and 1.96 million for Mexico. That makes Algeria the largest of the three and the largest country in Africa.
The key geographic reason is the Sahara: most of Algeria’s territory lies in the desert, including vast southern regions. Algeria became especially notable in area rankings after the independence of South Sudan in 2011, when it became Africa’s largest country.
A common mix-up is to assume Saudi Arabia is larger because it dominates the Arabian Peninsula. It is enormous, but Algeria still exceeds it by more than 200,000 square kilometres. Mexico is also large, yet remains smaller than both.