Gustave is a man-eating male Nile crocodile that roams the Ruzizi river and the northern shores of Lake Tanganyika in Burundi, Africa. Gustave is rumored to have killed as many as 200–300 people, but actual estimates put it up to 60 people. He has obtained a mythical status and is greatly feared by the people in the region.

Gustave was named by Patrice Faye, a herpetologist who has been studying him since the late 1990s. Much of what is known about Gustave stems from the film Capturing the Killer Croc, which aired in 2004 on PBS. The film documents an attempt to capture Gustave.

Gustave's exact length and weight are unknown. In 2002, National Geographic estimated he could be "easily more than 20 feet (6.1 m)" long, and weigh more than 2,000 pounds (907 kg). He is estimated to be over 60 years old and "still growing".

Gustave carries three bullet wound scars on his body. His right shoulder blade was also found to be deeply wounded. Circumstances surrounding the four scars are unknown. Scientists who have studied Gustave claim that his uncommon size and weight impede his ability to hunt the usual agile prey of Nile crocodiles such as fish, antelope and zebra, forcing him to attack larger animals such as hippopotamus, buffalo and humans. Despite frequently being referred to as a man-eater, a popular local warning says he often leaves his victims' corpses uneaten.

In Capturing the Killer Croc, Patrice Faye and other scientists attempted to capture Gustave over a period of two years. A trap cage weighing 2,000 pounds (907 kg) and measuring nearly 30 feet (9.1 m) in length was developed. The team then located Gustave, installed and baited the trap, also placing a hidden infrared camera inside. Several kinds of bait were used, yet none of them attracted Gustave or any other creature. The scientists then strategically installed three giant snares on certain banks to increase their chances of capture; although smaller crocodiles were caught by the traps, Gustave was not.

In the last week before being forced to leave the country due to an ongoing civil conflict, the team placed a live goat in the cage. As the result of a thunderstorm, the camera failed to operate and the following morning the cage was found partially submerged and the goat was gone. The team speculated that the rising waters helped the goat to escape or that the cage had failed, but without the camera recording, no conclusion could be drawn.

In 2009, Gustave appeared in the Ruzizi river near Lake Tanganyika.

In a 2019 article about travel in Burundi, a writer for Travel Africa Magazine reported learning that Gustave had been killed. It is not said how, where and by whom he was killed and no photographic evidence has ever surfaced, leaving these claims dubious until concrete evidence is brought forward.

Gustave was the basis of the film 2007 horror film Primeval (originally titled Gustave).

• Lolong, the largest crocodile in captivity until his death on February 10, 2013.