The Humboldt River is a large river in Liberty City featured in Grand Theft Auto IV which separates Algonquin Island from Broker, Dukes and Bohan, with Charge Island and Colony Island located on the river. It is named after the fictional explorer Horatio Humboldt.
The river is implied by the documentary "A History of Liberty City" to be heavily polluted before even the establishment of the city itself, due to the natives using it effectively as a sewer.
- The Humboldt River is based on two different rivers in New York City and Northern New Jersey. Its real life counterpart is the East River, which separates Manhattan and Long Island. The name "Humboldt" and the river's status as the main river in Liberty City is based on the Hudson River, which actually separates New York and New Jersey. It is not influenced by the real Humboldt River that runs through northern Nevada.
- The game makes many references to murderers and serial killers hiding the bodies of people they have killed, or want to kill, in this certain river.
- Niko Bellic executes Vladimir Glebov and disposes of his body in the Humboldt river during the mission Uncle Vlad.
- Niko also has the option of luring Dardan into the river and drowning him.
- Patrick McReary talks about dumping victims into the Humboldt in Undertaker, with Derrick or Francis' body.
- Dave Bosoy, who worked with Niko on the Platypus, is later said to be found dead on a Weazel News report. His body was found floating in the Humboldt wearing nothing but a diaper.
- Johnny Klebitz says the same thing in the mission Roman's Holiday, stating "I've seen some of the bodies you guys drop in the Humboldt" to the Russians.
- Because of the first meeting with Eddie Low, he may also use the Humboldt River to hide corpses.
- In Grand Theft Auto: Chinatown Wars, the protagonist, Huang Lee, is left for dead at the bottom of the river.
- A Tug Boat can be found under the Algonquin Bridge.
- The real Humboldt River runs through northern Nevada in the western United States.