Lake Maracaibo (Spanish: Lago de Maracaibo) is located in northwestern Venezuela, between the states of Zulia, Trujillo, and Mérida. While Maracaibo is commonly referred to as a lake, its current hydrological characteristics may better classify it as estuary and/or semi-enclosed bay connected to the Gulf of Venezuela. With a surface area of 13,512 km (5,217 sq mi), if counted as a lake it would be the largest in South America, ahead of Lake Titicaca, as well as one of the oldest lakes on Earth, having formed 36 million years ago in the Andes Mountains.
The lake consists of brackish water, and is connected to the Gulf of Venezuela to the north by a narrow strait. It is fed by numerous rivers, the biggest being the Catatumbo River. The fault in the northern section has collapsed and is rich in oil and gas resources. It is Venezuela's main oil producing area and an important fishing and agricultural producing area. Eutrophication caused by oil pollution is a major environmental problem facing the lagoon. The area around the lagoon is inhabited by a quarter of the country's population and is also the place with the most frequent lightning on Earth. The famous Catatumbo lightning can illuminate nighttime navigation.